Thermosetting type white coding with 100% solid content for metal printing and preparation method of thermosetting type white coding

Abstract

The invention discloses thermosetting type white coating with the solid content of 100% for metal printing and a preparation method of the thermosetting type white coating, and belongs to the technical field of primer for metal printing packaging. Comprising the following raw materials in parts by weight: 50-70 parts of thermosetting alicyclic epoxy resin, 5-15 parts of acrylic resin, 1-3 parts of blocked isocyanate, 3-5 parts of an alicyclic epoxy curing agent, 25-35 parts of a pigment, 1-5 parts of sulfydryl resin and 0.6-2.5 parts of an auxiliary agent. Meanwhile, the flexibility and the impact resistance of the paint film can be improved.

Description

Technical Field

[0001] This invention relates to the field of primers for tinplate packaging, and in particular to a thermosetting white phthalate with 100% solids content for tinplate printing and its preparation method. Background Technology

[0002] Tinplate and aluminum are commonly used packaging materials for tinplate packaging, widely applied in chemical drums, aerosol cans, beverage cans, milk powder cans, and many other fields. In industrial production, the printing process for tinplate packaging is crucial, and white primer, a key coating in the tinplate printing process, is the white base coat that comes into direct contact with the tinplate throughout the printing process. It plays an indispensable role in ensuring the quality and performance of tinplate packaging, and its quality and characteristics have received increasing attention and research in the development of the tinplate packaging industry.

[0003] In existing white coating technologies, the main curing methods are thermal curing and photocuring. Thermal curing, as the traditional and most widely used method in the white coating field, has significant advantages, such as enabling the coating to fully cure, ensuring coating performance, and providing deep curing layers, ensuring good curing results even with thicker coatings. It also has a relatively high curing speed. Photocuring, on the other hand, can alleviate some environmental problems to a certain extent, such as reducing related emissions in certain aspects. Currently, white coatings used in the tinplate packaging industry are mostly solvent-based, or mixed with solvents in small quantities.

[0004] However, existing white styrax technology has significant drawbacks. Solvent-based white styrax, or white styrax mixed with solvents, has high VOC emissions, failing to meet environmental protection requirements. While UV curing can solve the VOC emission problem, it does not achieve the performance of traditional thermosetting white styrax in terms of food safety or processing performance. Furthermore, UV curing requires modifying existing equipment and purchasing new equipment, resulting in large upfront investments. This leads to significant cost pressures and resource waste in large-scale industrial production. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a thermosetting white lacquer with 100% solid content for tinplate printing and its preparation method. By selecting raw materials, this application ensures that the VOC emission of white lacquer during curing is ≤2%, while also improving the flexibility and impact resistance of the coating film.

[0006] The first aspect of the present invention is to provide a 100% solids content thermosetting white benzoate for use in tinplate printing, employing the following technical solution: A 100% solids content thermosetting white phthalate for tinplate printing comprises the following raw materials in parts by weight: 50-70 parts thermosetting alicyclic epoxy resin, 5-15 parts acrylic resin, 1-3 parts blocked isocyanate, 3-5 parts alicyclic epoxy curing agent, 25-35 parts pigment, 1-5 parts mercapto resin, and 0.6-2.5 parts additives.

[0007] In a preferred embodiment, the white acetone comprises the following raw materials in parts by weight: 55-65 parts of thermosetting alicyclic epoxy resin, 10-15 parts of acrylic resin, 1-3 parts of blocked isocyanate, 3-5 parts of alicyclic epoxy curing agent, 25-35 parts of pigment, 2-4 parts of mercapto resin, and 0.6-2.5 parts of additives.

[0008] By employing the above technical solutions, thermosetting alicyclic epoxy resin exhibits high reactivity and good mechanical properties, while acrylic resin improves the flexibility and gloss of the resin system. The combination of these two components forms a paint film structure with a certain degree of flexibility. Blocked isocyanates, upon heating, unblock and participate in the reaction, increasing the crosslinking density and hardness of the paint film. This synergistic effect with the thermosetting alicyclic epoxy resin and acrylic resin further enhances the overall performance of the paint film. The alicyclic epoxy curing agent enables the thermosetting alicyclic epoxy resin to undergo a curing reaction, forming a stable three-dimensional network structure. The thiol resin, with its active thiol groups, reacts with the epoxy groups of the alicyclic epoxy resin, promoting more complete curing of the system under given baking conditions and forming a more uniform network. Furthermore, the large-scale introduction of thiol resin into the rigid epoxy network during curing effectively absorbs and disperses stress, making the paint film less prone to cracking during bending and stamping, thus contributing to improved adhesion and flexibility.

[0009] The leveling agent in the additives makes the paint film surface smooth and even, while the adhesion promoter enhances the adhesion between the paint film and the substrate. Since this white styrene is 100% solids and contains no organic solvents, it significantly reduces VOC emissions during use, keeping VOC emissions ≤2%. While reducing VOC emissions, the synergistic effect between the components improves the adhesion and flexibility of the paint film. Furthermore, the white styrene obtained in this application can be used in existing printing plant production lines without new investment, while also solving the VOC emission problem.

[0010] In a preferred embodiment, the mercapto resin is one or two of pentaerythritol-3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionate).

[0011] In a preferred embodiment, the weight ratio of pentaerythritol-3-mercaptopropionate to trimethylolpropane tris(3-mercaptopropionate) ester is 1:(0.5-1).

[0012] By adopting the above technical solution, when the mercapto resin is composed of pentaerythritol-3-mercaptopropionate and trimethylolpropane tri(3-mercaptopropionic acid) ester, the crosslinking density, the flexibility and impact resistance of the paint film can be better balanced. In addition, the introduction of trimethylolpropane tri(3-mercaptopropionic acid) ester can also reduce the viscosity of the system and improve the leveling and workability of white phthalate.

[0013] In a preferred embodiment, the additive is composed of a leveling agent and an adhesion promoter in a weight ratio of (0.1-0.5):(0.5-2.0).

[0014] In a preferred embodiment, the leveling agent is an acrylate leveling agent.

[0015] In a preferred embodiment, the pigment is a modified pigment obtained by modifying a titanate coupling agent.

[0016] In a preferred embodiment, the modified pigment is obtained by the following modification method: dissolving a titanate coupling agent in a solvent, adding the pigment under high-speed stirring, heating to 90-100°C and stirring for 40-50 minutes, and then cooling and drying to obtain the modified pigment.

[0017] By adopting the above technical solution, after modifying the pigment with a titanate coupling agent, long titanate chains are grafted onto the pigment surface, generating a steric hindrance effect between particles, which effectively prevents the dispersed pigment from flocculating or settling again during construction, thereby maintaining the dispersion stability of the system.

[0018] A second aspect of the present invention is to provide a method for preparing 100% solid content thermosetting white benzoin for printing as described above, comprising the following steps: S1. Mix 50% by weight of thermosetting alicyclic epoxy resin and 50% by weight of acrylic resin, and stir to dissolve at 80-85°C to obtain intermediate I; S2. Mix 50% by weight of blocked isocyanate with 50% by weight of thermosetting alicyclic epoxy resin, and stir to dissolve at 80-85°C to obtain intermediate II; S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed for 50-60 minutes to obtain thermosetting white benzoin.

[0019] In a preferred embodiment, the stirring speed in step S3 is 1400-1600 r / min.

[0020] By adopting the above technical solution, the preparation method first mixes some raw materials to obtain intermediate I and intermediate II, and then mixes the two with the remaining substances, which helps the components to fully dissolve and react, improves the uniformity and stability of the reaction, and obtains a thermosetting white cadmium with 100% solid content. Because the white cadmium adopts a thermosetting method, it has the advantages of high curing speed, full curing of coating to ensure coating performance, and deep curing layer to ensure good curing of thicker coatings. At the same time, the 100% solid content can solve the problem of high VOC emissions of existing solvent-based white cadmium.

[0021] In summary, the present invention has the following beneficial effects: 1. This thermosetting white benzoate has a 100% solid content, which can solve the problem of high VOC emissions in existing solvent-based white benzoate or white benzoate mixed with solvents, and meet environmental protection requirements; 2. The thermosetting method allows the coating to fully cure, ensuring the performance of the coating layer. It also provides a deep curing layer, ensuring good curing results even when the coating is thick. 3. No need to modify existing equipment or purchase new equipment, avoiding the problem of high costs associated with UV curing. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments. All reagents, unless otherwise specified, are commercially available conventional reagent products.

[0023] Preparation Example 1 A method for modifying a modified pigment includes the following steps: The titanate coupling agent (CAS No.: 65467-75-6) was dissolved in toluene, and rutile titanium dioxide was added under high-speed stirring. The temperature was raised to 90°C and stirred for 50 minutes. Then the mixture was cooled and dried to obtain the modified pigment. The amount of titanate coupling agent added was 3% of the weight of rutile titanium dioxide.

[0024] Preparation Example 2 A method for modifying a modified pigment includes the following steps: The titanate coupling agent (CAS No.: 65467-75-6) was dissolved in toluene, and rutile titanium dioxide was added under high-speed stirring. The temperature was raised to 100℃ and stirred for 40 min. Then the mixture was cooled and dried to obtain the modified pigment. The amount of titanate coupling agent added was 2% of the weight of rutile titanium dioxide.

[0025] Example 1 A 100% solids content thermosetting white benzoate for use in tinplate printing comprises the following raw materials: 5 kg of thermosetting alicyclic epoxy resin, 0.5 kg of acrylic solid resin, 0.1 kg of blocked isocyanate, 0.3 kg of alicyclic epoxy curing agent, 2.5 kg of rutile titanium dioxide, 0.1 kg of mercapto resin, and 0.06 kg of additives; The mercapto resin used is pentaerythritol-3-mercaptopropionate; The thermosetting alicyclic epoxy resin was purchased from Yantai Donghua New Materials, model DE322; The acrylic solid resin (100% solids content) was purchased from Inovance LP-51; Blocked isocyanate (100% solids content) was purchased from Ingenic 1358; The alicyclic epoxy curing agent was purchased from Yantai Donghua New Materials, model XE0506; The additive consists of an acrylate leveling agent and an adhesion promoter in a weight ratio of 0.1:0.5; Acrylic leveling agent was purchased from BYK-35BN by BYK Chemicals; The adhesion promoter is Zhanxin Chemical 168; Its preparation method includes the following steps: S1. Mix 2.5 kg of thermosetting alicyclic epoxy resin with 0.25 kg of acrylic resin and stir to dissolve at 80 °C to obtain intermediate I; S2. Mix 0.05 kg of blocked isocyanate with 2.5 kg of thermosetting alicyclic epoxy resin and stir to dissolve at 80 °C to obtain intermediate II; S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed of 1400 r / min for 60 min to obtain thermosetting white benzoin with a fineness of <2.5 μm.

[0026] Example 2 A 100% solids content thermosetting white benzoate for use in tinplate printing comprises the following raw materials: 5.5 kg of thermosetting alicyclic epoxy resin, 1 kg of acrylic solid resin, 0.2 kg of blocked isocyanate, 0.4 kg of alicyclic epoxy curing agent, 3 kg of rutile titanium dioxide, 0.2 kg of mercapto resin, and 0.15 kg of additives; The mercapto resin used is pentaerythritol-3-mercaptopropionate; The thermosetting alicyclic epoxy resin was purchased from Yantai Donghua New Materials, model DE322; The acrylic solid resin (100% solids content) was purchased from Inovance LP-51; Blocked isocyanate (100% solids content) was purchased from Ingenic 1358; The alicyclic epoxy curing agent was purchased from Yantai Donghua New Materials, model XE0506; The additive consists of an acrylate leveling agent and an adhesion promoter in a weight ratio of 0.3:1.5; Acrylic leveling agent was purchased from BYK-35BN by BYK Chemicals; The adhesion promoter is Zhanxin Chemical 168; Its preparation method includes the following steps: S1. Mix 2.75 kg of thermosetting alicyclic epoxy resin with 0.5 kg of acrylic solid resin and stir to dissolve at 85 °C to obtain intermediate I; S2. Mix 0.1 kg of blocked isocyanate with 2.75 kg of thermosetting alicyclic epoxy resin and stir to dissolve at 85 °C to obtain intermediate II; S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed of 1500 r / min for 60 min to obtain thermosetting white benzoin with a fineness of <2.5 μm.

[0027] Example 3 A 100% solids content thermosetting white benzoate for use in tinplate printing comprises the following raw materials: Thermosetting alicyclic epoxy resin 6.5kg, acrylic solid resin 1kg, blocked isocyanate 0.2kg, alicyclic epoxy curing agent 0.4kg, rutile titanium dioxide 3kg, mercapto resin 0.4kg, and additives 0.2kg; The mercapto resin used is pentaerythritol-3-mercaptopropionate; The thermosetting alicyclic epoxy resin was purchased from Yantai Donghua New Materials, model DE322; The acrylic solid resin (100% solids content) was purchased from Inovance LP-51; Blocked isocyanate (100% solids content) was purchased from Ingenic 1358; The alicyclic epoxy curing agent was purchased from Yantai Donghua New Materials, model XE0506; The additive consists of an acrylate leveling agent and an adhesion promoter in a weight ratio of 0.3:1; Acrylic leveling agent was purchased from BYK-35BN by BYK Chemicals; The adhesion promoter is Zhanxin Chemical 168; Its preparation method includes the following steps: S1. Mix 3.25 kg of thermosetting alicyclic epoxy resin with 0.5 kg of acrylic solid resin and stir to dissolve at 80 °C to obtain intermediate I; S2. Mix 0.1 kg of blocked isocyanate with 3.25 kg of thermosetting alicyclic epoxy resin and stir to dissolve at 80 °C to obtain intermediate II; S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed of 1500 r / min for 60 min to obtain thermosetting white benzoin with a fineness of <2.5 μm.

[0028] Example 4 A 100% solids content thermosetting white benzoate for use in tinplate printing comprises the following raw materials: 7 kg of thermosetting alicyclic epoxy resin, 1.5 kg of acrylic solid resin, 0.3 kg of blocked isocyanate, 0.5 kg of alicyclic epoxy curing agent, 3.5 kg of rutile titanium dioxide, 0.5 kg of mercapto resin, and 0.25 kg of additives; The mercapto resin used is pentaerythritol-3-mercaptopropionate; The thermosetting alicyclic epoxy resin was purchased from Yantai Donghua New Materials, model DE322; The acrylic solid resin (100% solids content) was purchased from Inovance LP-51; Blocked isocyanate (100% solids content) was purchased from Ingenic 1358; The alicyclic epoxy curing agent was purchased from Yantai Donghua New Materials, model XE0506; The additive consists of an acrylate leveling agent and an adhesion promoter in a weight ratio of 0.3:1; Acrylic leveling agent was purchased from BYK-35BN by BYK Chemicals; The adhesion promoter is Zhanxin Chemical 168; Its preparation method includes the following steps: S1. Mix 3.5 kg of thermosetting alicyclic epoxy resin with 0.75 kg of acrylic solid resin and stir to dissolve at 80 °C to obtain intermediate I; S2. Mix 0.15 kg of blocked isocyanate with 3.5 kg of thermosetting alicyclic epoxy resin and stir to dissolve at 80 °C to obtain intermediate II; S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed of 1500 r / min for 60 min to obtain thermosetting white benzoin with a fineness of <2.5 μm.

[0029] Example 5 A 100% solids content thermosetting white benzoin for printing iron differs from Example 3 in that the mercapto resin is trimethylolpropane tris(3-mercaptopropionic acid) ester, otherwise it is the same as Example 3.

[0030] Example 6 A thermosetting white styrene with 100% solids content for use in tinplate printing differs from Example 3 in that the total amount of thiol resin is 0.4 kg, and the thiol resin is composed of pentaerythritol-3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionic acid) ester in a weight ratio of 1:0.5. All other aspects are the same as in Example 3.

[0031] Example 7 A thermosetting white styrene with 100% solids content for use in tinplate printing differs from Example 3 in that the total amount of thiol resin is 0.4 kg, and the thiol resin is composed of pentaerythritol-3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionic acid) ester in a weight ratio of 1:1. All other aspects are the same as in Example 3.

[0032] Example 8 A 100% solids content thermosetting white tartaric acid for printing iron differs from Example 7 in that the rutile titanium dioxide is prepared using the modified pigment obtained in Preparation Example 1, while all other aspects are the same as in Example 7.

[0033] Example 9 A 100% solids content thermosetting white tartaric acid for printing iron differs from Example 7 in that the rutile titanium dioxide is made from the modified pigment obtained in Preparation Example 2, while all other aspects are the same as in Example 7.

[0034] Comparative Example 1 A thermosetting white phenolic resin with 100% solids content for use in tinplate printing differs from Example 2 in that the raw material does not contain thiol resin, but is otherwise the same as Example 2.

[0035] Comparative Example 2 A 100% solids content thermosetting white phenolic resin for printing iron differs from Example 2 in that it does not contain acrylic solid resin in the raw materials, but is otherwise the same as Example 2.

[0036] Performance testing The white phthalate obtained from the above examples and comparative examples was uniformly coated on tinplate with a wet film thickness of 10 μm. After baking in an oven at 160°C for 10 min, the gloss, adhesion, flexibility, impact resistance, and solvent resistance of the paint film were tested. The test results are shown in Table 1.

[0037] Adhesion was tested in accordance with the relevant provisions of GB / T9286 "Paints and Varnishes Cross-cut Test".

[0038] The drop ball impact test shall be conducted in accordance with the relevant provisions of GB / T 20624.1 "Rapid Deformation Tests of Paints and Varnishes - Part 1: Drop Weight Test".

[0039] Solvent resistance is tested by repeatedly wiping the paint film surface with a cotton ball soaked in ethanol, and recording the number of wipings before the paint film is damaged (such as wrinkling or dissolution).

[0040] The flexibility test involves placing an oiled tinplate on a shaft of different diameters and bending it 180° to test the flexibility of the coating. The smallest shaft is the one that allows the coating to remain intact after bending; the diameter in millimeters is the evaluation value of the flexibility.

[0041] Table 1. Test Results of White Coating Film Performance Note: The 50cm kg in impact resistance refers to the impact resistance of the paint film sample when it is dropped freely from a height of 50cm using a 1kg hammer without damage. The principle is the same for 50cm 2kg, 30cm kg, and 35cm kg.

[0042] The VOC emissions during curing of the white cod obtained in the embodiments and comparative examples of this application are all ≤2%.

[0043] Based on the test data in Table 1: The gloss of the white caustic soda film obtained in Examples 1-4 of this application is all above 80, the adhesion is all below grade 0, the flexibility is such that no cracking occurs after bending 180° on a 10mm diameter shaft, the solvent resistance is 10 cycles, and the impact resistance is 50cm kg. This indicates that the white caustic soda obtained in Examples 1-4 of this application has good adhesion, flexibility and impact resistance.

[0044] Compared with Example 3, when the mercapto resin is trimethylolpropane tri(3-mercaptopropionic acid) ester, the flexibility of Example 5 is improved compared with Example 3. It can be bent 180° on a shaft with a diameter of 8mm without cracking, indicating that the flexibility of the paint film is further improved after using trimethylolpropane tri(3-mercaptopropionic acid) ester.

[0045] Compared with Example 3, when the mercapto resin is composed of pentaerythritol-3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionic acid) ester, the flexibility and impact resistance of the paint film obtained in Examples 6-7 are significantly improved compared with Example 3. It can be seen that the combined use of the two mercapto resins can effectively improve the flexibility of the paint film.

[0046] Compared with Example 7, when titanium dioxide modified with titanate coupling agent is used, the flexibility, solvent resistance and impact resistance of Examples 8-9 are significantly improved compared with Example 7. It can be seen that after the pigment is modified with titanate coupling agent, it can be more evenly dispersed in the resin, which improves the color of the paint film, the gloss is better, and the solvent resistance is also further improved.

[0047] Compared with Example 2, when the raw materials lack thiol resin or acrylic solid resin, the adhesion, flexibility, and impact resistance of the paint film decrease, while the solvent resistance increases. The reason is that when the paint film lacks thiol resin or acrylic solid resin, the rigidity and internal stress of the paint film increase. When subjected to deformation, the stress is more likely to concentrate at the interface, resulting in a decrease in adhesion, flexibility, and impact resistance. Since the addition of thiol resin and acrylic solid resin slightly reduces the density of the paint film crosslinking network, the flexibility will be improved. When either thiol resin or acrylic solid resin is lacking, the density of the paint film crosslinking network will be further improved, so the resistance to solvent erosion will be better.

[0048] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A 100% solids content thermosetting white benzoate for use in tinplate printing, characterized in that, The raw materials include the following parts by weight: 50-70 parts of thermosetting alicyclic epoxy resin, 5-15 parts of acrylic resin, 1-3 parts of blocked isocyanate, 3-5 parts of alicyclic epoxy curing agent, 25-35 parts of pigment, 1-5 parts of mercapto resin, and 0.6-2.5 parts of additives.

2. The thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 1, characterized in that: The white acetone comprises the following raw materials in parts by weight: 55-65 parts of thermosetting alicyclic epoxy resin, 10-15 parts of acrylic resin, 1-3 parts of blocked isocyanate, 3-5 parts of alicyclic epoxy curing agent, 25-35 parts of pigment, 2-4 parts of mercapto resin, and 0.6-2.5 parts of additives.

3. A thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 1 or 2, characterized in that: The mercapto resin is one or two of pentaerythritol-3-mercaptopropionate and trimethylolpropane tris(3-mercaptopropionate).

4. The thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 3, characterized in that: The weight ratio of pentaerythritol-3-mercaptopropionate to trimethylolpropane tris(3-mercaptopropionate) ester is 1:(0.5-1).

5. The thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 1, characterized in that: The additive is composed of a leveling agent and an adhesion promoter in a weight ratio of (0.1-0.5):(0.5-2.0).

6. The thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 5, characterized in that: The leveling agent used is an acrylate leveling agent.

7. The thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 1, characterized in that: The pigment is a modified pigment, which is obtained by modifying a titanate coupling agent.

8. A thermosetting white benzoin with 100% solid content for use in tinplate printing according to claim 7, characterized in that: The modified pigment is obtained by the following modification method: dissolving the titanate coupling agent in a solvent, adding the pigment under high-speed stirring, heating to 90-100℃ and stirring for 40-50 minutes, and then cooling and drying to obtain the modified pigment.

9. A method for preparing 100% solid content thermosetting white benzoate for printing as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Mix 50% by weight of thermosetting alicyclic epoxy resin and 50% by weight of acrylic resin, and stir to dissolve at 80-85℃ to obtain intermediate I. S2. Mix 50% by weight of blocked isocyanate with 50% by weight of thermosetting alicyclic epoxy resin, and stir to dissolve at 80-85°C to obtain intermediate II. S3. Mix intermediate I, intermediate II and all remaining substances, and disperse at high speed for 50-60 minutes to obtain thermosetting white benzoin.

10. A method for preparing 100% solid content thermosetting white benzoin for printing according to claim 9, characterized in that: The stirring speed in step S3 is 1400-1600 r / min.

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