Special coating for electron beam curing as well as preparation method and application thereof

Abstract

The invention discloses a special coating for electron beam curing as well as a preparation method and application thereof, and belongs to the field of radiation curing materials. According to the coating, hyperbranched polyester acrylate and urethane acrylate in a specific proportion are used as oligomer resin compositions, and the oligomer resin compositions are matched with a composite reactive diluent composed of isobornyl methacrylate (IBOA) and 1, 6-hexanediol diacrylate (HDDA) and surface-modified fumed silica, so that the coating is prepared. The composition comprises the following components in parts by mass: 45-65 parts of an oligomer resin composition; 25 to 40 parts of a reactive diluent; 5 to 15 parts of functional filler; and 0.5-3 parts of an auxiliary agent. The coating disclosed by the invention has the characteristics of low viscosity and high reaction activity, a cured coating is excellent in adhesive force, perfect balance of high hardness and high flexibility is realized, and the coating is particularly suitable for coating protection of non-porous base materials such as metal, plastic and the like with strict adhesive force and requirements.

Description

Technical Field

[0001] This invention belongs to the field of radiation curing materials technology, specifically an electron beam curing coating, its preparation method, and its application. Background Technology

[0002] Electron beam curing (EB) is a highly efficient and green curing technology that uses a high-energy electron beam to instantly initiate the polymerization reaction of active monomers and oligomers in a formulation at room temperature, forming a cross-linked network structure. Compared with traditional UV curing, EB curing has advantages such as strong penetration (it can cure colored coatings and opaque formulations), no need for photoinitiators (PI-free), thorough curing, and no small molecule residues. It has broad application prospects in high-end wood products, metal packaging, automobiles, and electronic products.

[0003] However, EB curing technology has specific requirements for coating formulations, which constitutes a bottleneck for existing technologies: High reactivity requirement: Electron beam (EB) curing relies entirely on electron beam energy to directly break carbon-carbon double bonds to generate free radicals for polymerization. Therefore, the formulation system must contain a high concentration of highly reactive carbon-carbon double bonds (such as acrylate functional groups). Conventional UV-curable resins (such as epoxy acrylates and polyurethane acrylates) may have insufficient reactivity under EB, resulting in slow curing speed or low conversion rate.

[0004] Volume shrinkage and adhesion issues: Although high-functionality monomers / oligomers can increase the curing speed, they will cause significant polymerization volume shrinkage, resulting in decreased adhesion to substrates such as metals and plastics and increased internal stress.

[0005] Balancing flexibility and hardness: Many EB-cured coatings, while achieving high hardness and scratch resistance, sacrifice flexibility and impact resistance, making them difficult to meet the requirements of certain applications.

[0006] The contradiction between low viscosity and high functionality: In order to obtain good application leveling properties and avoid the use of large amounts of reactive diluents, it is necessary to develop resins that have low viscosity and high functionality. Summary of the Invention

[0007] To address the deficiencies and shortcomings of the prior art, this invention provides an electron beam curing coating that simultaneously achieves extremely high EB curing reactivity for deep and rapid curing; excellent adhesion, especially on non-porous substrates (such as PET, PC, and aluminum); a remarkable balance between hardness and flexibility, resulting in a coating that is both hard and tough, impact-resistant, and bend-resistant; low viscosity, high solids content, easy to apply, and extremely low VOC content; good storage stability and pigment compatibility; and its preparation method and application.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a special coating for electron beam curing, comprising a connector body and an adapter, and composed of the following components in parts by weight: Oligopolymer resin composition: 45-65 parts; Reactive diluent: 25-40 parts; Functional filler: 5-15 parts; Additives: 0.5-3 parts; The oligomer resin composition is made by compounding hyperbranched polyester acrylate (HBP-Acrylates) and polyurethane acrylate (PUA) in a mass ratio of (1:1) to (1:0.6).

[0009] Preferably, the hyperbranched polyester acrylate is a product of the Boltorn™ series of hyperbranched polyester modified by acrylate esterification. Its three-dimensional spherical structure can provide low viscosity and high functionality, effectively reducing the overall viscosity of the system, reducing the amount of diluent, and giving the formulation extremely high electron beam curing reactivity due to its large number of terminal double bonds.

[0010] Preferably, the polyurethane acrylate is selected as fatty acid modified polyurethane acrylate, whose flexible segments and urethane bonds in the molecular chain can effectively improve the flexibility and adhesion of the coating, and work synergistically with hyperbranched resin to perfectly balance the hardness and flexibility of the coating.

[0011] Preferably, the active diluent is a composite system of monofunctional and difunctional acrylates, specifically composed of isobornyl methacrylate (IBOA) and 1,6-hexanediol diacrylate (HDDA) in a mass ratio of (2:1) to (1:1).

[0012] IBOA: A monofunctional monomer with a large, rigid ring structure. It exhibits minimal volume shrinkage during curing, significantly improving adhesion to non-porous substrates (such as PET, PC, and metals) and imparting excellent weather resistance to the coating.

[0013] HDDA: A bifunctional monomer that provides a moderate crosslinking density to ensure curing speed. At the same time, its long carbon chain structure does not significantly increase the viscosity of the system and contributes to flexibility.

[0014] Preferably, the functional filler is fumed silica surface-modified with a silane coupling agent, and the addition amount is 3-8 parts.

[0015] Preferably, the additives include leveling agents and defoamers, and a small amount of pigments or ultraviolet absorbers may be added as needed. The leveling agent is selected from polyether-modified polysiloxanes (such as BYK-333), and the defoamer is selected from non-silicones (such as BYK-055).

[0016] A method for preparing a special coating for electron beam curing, comprising the following steps: S1. Premixing: Under light-protected conditions, add HBP, PUA, IBOA and HDDA to an adjustable speed dispersion vessel and stir at 300-500 rpm for 15 minutes until the mixture is homogeneous. S2. Filler dispersion: Slowly add fumed silica, increase the stirring speed to 1500-2000 rpm, disperse at high speed for 30 minutes, and use shear force to fully wet and disperse the nanofiller; S3. Conditioning and Defoaming: Reduce the rotation speed to 500 rpm, add leveling agent and defoamer, and continue stirring for 10 minutes. Then transfer the liquid to a vacuum defoamer and defoam for 15 minutes under a vacuum of -0.095 MPa to obtain a uniform, transparent, and bubble-free electron beam cured coating.

[0017] Preferably, in a method for preparing an electron beam curable coating, when preparing a high-gloss white coating, after step S1, titanium dioxide is first added and dispersed at high speed at 1500 rpm for 30 minutes, and then steps S2 and S3 are performed.

[0018] Preferably, in a method for preparing an electron beam curable coating, when preparing a matte black coating, after step S1, 3 parts of matting powder (TS-100) and 2 parts of carbon black paste are first added and dispersed at high speed at 1500 rpm for 30 minutes, and then steps S2 and S3 are performed.

[0019] Preferably, an electron beam curing coating is used in the coating of metal, plastic or wood surfaces.

[0020] The coating prepared by this invention must simultaneously meet the following requirements: extremely high EB curing reactivity to achieve deep and rapid curing; excellent adhesion, especially on non-porous substrates (such as PET, PC, and aluminum); excellent balance between hardness and flexibility, making the coating both hard and tough, impact-resistant and bend-resistant; low viscosity, high solids content, easy to apply and extremely low VOC content; good storage stability and pigment compatibility. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, but this is not intended to limit the scope of protection of the present invention. Example 1

[0023] A method for preparing an electron beam curable coating includes the following steps (e.g.) Figure 1 (as shown) S1. Premixing: The oligomer resin composition and the reactive diluent are mixed evenly under stirring; S2. Filler dispersion: Add functional fillers to the mixture from step S1 and disperse them at high speed. S3. Conditioning and Degassing: Add additives, stir and condition, then perform vacuum degassing to obtain the coating. Example 2

[0024] The present invention prepares the clear topcoat as follows: Raw material ratio (by mass): Hyperbranched polyester acrylate (HBP): 25 parts Fatty acid modified polyurethane acrylate (PUA): 25 parts Isoborneol methacrylate (IBOA): 20 parts 1,6-Hexanediol diacrylate (HDDA): 10 parts Fumed silica (Aerosil R202): 4 parts Leveling agent (BYK-333): 0.3 parts Defoamer (BYK-055): 0.2 parts The preparation process is as follows: S1. Premixing: Under light-protected conditions, add HBP, PUA, IBOA and HDDA to an adjustable speed dispersion vessel and stir at 300-500 rpm for 15 minutes until the mixture is homogeneous.

[0025] S2. Filler dispersion: Slowly add fumed silica, increase the stirring speed to 1500-2000 rpm, and disperse at high speed for 30 minutes to fully wet and disperse the nanofiller using shear force.

[0026] S3. Conditioning and Defoaming: Reduce the rotation speed to 500 rpm, add leveling agent and defoamer, and continue stirring for 10 minutes. Then transfer the liquid to a vacuum defoamer and defoam for 15 minutes under a vacuum of -0.095 MPa to obtain a uniform, transparent, and bubble-free electron beam cured coating. Example 3

[0027] The high-gloss white coating prepared by this invention is as follows: Based on Example 1, 5 parts of rutile titanium dioxide (pre-treated with 2% silane coupling agent KH-570) were added. During preparation, after step a, the titanium dioxide was first added and dispersed at high speed (1500 rpm, 30 minutes), followed by steps b and c. This formulation is suitable for applications requiring both hiding power and decorative properties. Example 4

[0028] The matte black coating prepared by this invention is as follows: Based on Example 1, 3 parts of matte powder (TS-100) and 2 parts of carbon black paste were added. The preparation process was the same as in Example 2. This formulation yields a high-quality matte black coating.

[0029] Comparative Example To highlight the advantages of the present invention, a comparative example was set up: 40 parts of conventional epoxy acrylate (EA) were used instead of the HBP / PUA resin composition of the present invention, and the remaining components and amounts were exactly the same as in Example 1.

[0030] Performance Testing and Beneficial Effects The coatings obtained from the above examples and comparative examples were applied to birch veneer multilayer engineered wood panels and PC plastic panels using a 100μm wire bar coater, and then cured under nitrogen protection (oxygen concentration <500 ppm) using an electron beam curing device (accelerating voltage 170 kV, dose 40 kGy).

[0031] The test results are as follows: Results analysis and the beneficial effects of the present invention: Excellent balance between adhesion and flexibility: Example 1 achieved Grade 0 adhesion on both multilayer engineered wood panels and PC boards, and its impact resistance and T-bending performance were far superior to the comparative example. This demonstrates that the HBP / PUA / IBOA combination can effectively reduce polymerization stress and enhance the adhesion between the coating and the substrate.

[0032] High hardness and high toughness coexist: Example 1, while maintaining the high hardness of 3H, passed the 50 kg·cm impact test, demonstrating the perfect synergy between the rigid core of the hyperbranched resin and the flexible chain of polyurethane.

[0033] Low viscosity and high workability: The viscosity of the formulation of this invention is only 850 mPa·s, which is much lower than that of the comparative example. It is easy to level, spray or roll, and no additional solvent is required. It truly achieves ultra-high solids content and ultra-low VOC.

[0034] Extremely high curing reactivity: Under the same electron beam dosage, the coating of this invention can achieve "instant drying" and the curing speed is significantly faster than that of the comparative example, which proves that its double bond reactivity is higher and is beneficial to improving production efficiency.

[0035] The coating of the present invention has high reactivity, ultra-low volatile organic compound (VOC) emissions, excellent substrate adhesion and cured film performance, and is particularly suitable for electron beam (EB) curing.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A special coating for electron beam curing, comprising a connector body and an adapter, characterized in that: It consists of the following components in parts by mass: Oligopolymer resin composition: 45-65 parts; Reactive diluent: 25-40 parts; Functional filler: 5-15 parts; Additives: 0.5-3 parts; The oligomer resin composition is made by compounding hyperbranched polyester acrylate (HBP-Acrylates) and polyurethane acrylate (PUA) in a mass ratio of (1:1) to (1:0.6).

2. The electron beam curing coating according to claim 1, characterized in that: The hyperbranched polyester acrylate is a product of the Boltorn™ series of hyperbranched polyesters modified by acrylate esterification. Its three-dimensional spherical structure provides low viscosity and high functionality, effectively reducing the overall viscosity of the system, reducing the amount of diluent used, and endowing the formulation with extremely high electron beam curing reactivity due to its large number of terminal double bonds.

3. The electron beam curing coating according to claim 2, characterized in that: The polyurethane acrylate is selected as fatty acid modified polyurethane acrylate. The flexible segments and urethane bonds in its molecular chain can effectively improve the flexibility and adhesion of the coating. It works synergistically with hyperbranched resin to perfectly balance the hardness and flexibility of the coating.

4. The electron beam curing coating according to claim 1, characterized in that: The active diluent is a composite system of monofunctional and difunctional acrylates, specifically composed of isobornyl methacrylate (IBOA) and 1,6-hexanediol diacrylate (HDDA) in a mass ratio of (2:1) to (1:1).

5. The electron beam curing coating according to claim 1, characterized in that: The functional filler is fumed silica with a surface modified by a silane coupling agent, and the addition amount is 3-8 parts.

6. The electron beam curing coating according to claim 1, characterized in that: The additives include leveling agents and defoamers. A small amount of pigments or ultraviolet absorbers may be added as needed. The leveling agent is selected from polyether-modified polysiloxanes, and the defoamer is selected from non-silicone compounds.

7. A method for preparing an electron beam curable coating as described in claim 1, characterized in that: The steps are as follows: S1. Premixing: Under light-protected conditions, add HBP, PUA, IBOA and HDDA to an adjustable speed dispersion vessel and stir at 300-500 rpm for 15 minutes until the mixture is homogeneous. S2. Filler dispersion: Slowly add fumed silica, increase the stirring speed to 1500-2000 rpm, disperse at high speed for 30 minutes, and use shear force to fully wet and disperse the nanofiller; S3. Conditioning and Defoaming: Reduce the rotation speed to 500 rpm, add leveling agent and defoamer, and continue stirring for 10 minutes. Then transfer the liquid to a vacuum defoamer and defoam for 15 minutes under a vacuum of -0.095 MPa to obtain a uniform, transparent, and bubble-free electron beam cured coating.

8. The method for preparing the electron beam curing coating according to claim 7, characterized in that: When preparing a high-gloss white coating, after step S1, titanium dioxide is first added and dispersed at high speed at 1500 rpm for 30 minutes, and then steps S2 and S3 are performed.

9. The method for preparing an electron beam curable coating according to claim 7, characterized in that: When preparing a matte black coating, after step S1, add 3 parts of matting powder (TS-100) and 2 parts of carbon black paste for high-speed dispersion at 1500 rpm for 30 minutes, and then proceed to steps S2 and S3.

10. The application of an electron beam curing coating as described in any one of claims 1-6 in the coating of metal, plastic or wood surfaces.

Images