A resin anti-aging treatment method based on ultraviolet absorption gradient distribution

Abstract

This invention relates to the field of polymer surface treatment and functional modification technology, specifically to a resin anti-aging treatment method based on ultraviolet absorption gradient distribution. It includes the following steps: S1: preparing a gradient coating solution; S2: high-concentration initial coating, gradient transition treatment, low-concentration touch-up coating, and complete curing. A continuous gradient distribution is achieved: through a specific sequence of "high-concentration initial coating → transition treatment → low-concentration touch-up coating," combined with low-temperature pre-curing control at 40-60℃, a continuous concentration gradient of the ultraviolet-absorbing functional components from the surface to the interior is successfully constructed. The surface concentration is high, and the interior concentration is low, with mutual solubility between layers and no clear interface. Strong surface ultraviolet resistance: the concentration of ultraviolet absorber in the 0-50μm region of the surface is 3-10 times that of the interior region, efficiently absorbing ultraviolet light entering the surface and protecting the deeper resin from damage. High internal transparency: the internal ultraviolet absorber content is low, and the resin transmittance is ≥90%, avoiding the scattering and absorption of visible light by additives in uniformly distributed solutions.

Description

Technical Field

[0001] This invention relates to the field of polymer material surface treatment and functional modification technology, specifically to a resin anti-aging treatment method based on ultraviolet absorption gradient distribution. Background Technology

[0002] Resin materials are prone to yellowing under light exposure, primarily because ultraviolet (UV) radiation causes the resin molecular chains to break and generate chromophores. A common method to address this problem is to add UV absorbers to the resin. However, UV damage to resin is mainly concentrated in the surface 0-50 μm region, while current technologies typically use blending to uniformly disperse the UV absorber throughout the resin matrix, which has the following drawbacks:

[0003] 1. Waste of function: The UV absorbers in the internal area contribute almost nothing to the UV protection of the surface layer, resulting in increased costs.

[0004] 2. Decreased transparency: The presence of a large amount of UV absorber inside the material scatters or absorbs visible light, reducing the overall transparency of the material. Existing blending solutions typically have a light transmittance of less than 80% at effective anti-yellowing levels.

[0005] 3. Insufficient surface protection: The amount added by the blending method is limited (too much will affect the overall transparency), the concentration of UV absorber on the surface is not enough, and the surface layer is still prone to aging.

[0006] 4. Fine textures are filled in: Existing surface coating processes (such as spraying, brushing, and direct curing after dipping) often form an additional coating on the resin surface, filling in existing fine textures (such as skin pores and muscle lines), which cannot meet the requirements of BJD and other fine crafts for preserving micron-level textures.

[0007] A search revealed that while existing technologies may include multi-layer coatings or surface modification methods, these are fundamentally different from the technical approach of this invention.

[0008] Patent CN116970192A (Surface modified component and manufacturing method thereof) discloses a surface modified layer stacked on a resin component, with a mixed layer between the layers, but the overall structure is still a discrete layered structure with interlayer interfaces.

[0009] Patent CN115826300A (low-reflection anti-yellowing resin lens) uses a multi-layer coating (hardening layer, low-reflection coating layer, waterproof layer), which is a typical discrete multi-layer structure.

[0010] Chiguard® R-455 solution from Chitai Technology covalently grafts UV absorbers onto the resin matrix through chemical bonding. This method requires chemical modification of the resin, is complex and has poor universality, and the transmittance can only be maintained at 65% at high addition levels.

[0011] Currently, there is no process that can simply and efficiently achieve a continuous gradient distribution of UV absorbers with "high concentration on the surface and low concentration inside" in resin materials, while retaining 100% of the fine surface texture.

[0012] Therefore, in order to solve the above problems, a resin anti-aging treatment method based on ultraviolet absorption gradient distribution is provided. Summary of the Invention

[0013] The present invention aims to provide a resin anti-aging treatment method based on ultraviolet absorption gradient distribution, which solves the problems of high cost, low transparency, insufficient surface protection and easy filling of surface texture caused by uniform distribution of ultraviolet absorbers in the prior art, and achieves the unity of anti-yellowing performance, transparent texture and fine texture.

[0014] Technical solution

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] A resin anti-aging treatment method based on ultraviolet absorption gradient distribution, characterized by comprising the following steps:

[0017] S1: Preparation of gradient dip coating solution:

[0018] Prepare a first-concentration dipping coating solution (high-concentration solution). The first-concentration dipping coating solution contains ultraviolet absorption functional components, dispersed in an organic solvent, with a solid content of 10%-25%.

[0019] Prepare a second concentration immersion coating solution (low concentration solution), wherein the solid content of the ultraviolet absorption functional component in the second concentration immersion coating solution is 20%-40% of that in the first concentration immersion coating solution;

[0020] S2: High-concentration initial coating: Immerse the uncured resin blank in the first concentration coating solution and perform low-temperature pre-curing at 40-60℃ for 5-20 minutes to form a high-concentration penetration layer of UV absorption functional components on the surface of the resin blank.

[0021] S3: Gradient transition treatment: Immerse the resin preform after step (2) into a mixture of first concentration dipping solution and second concentration dipping solution (volume ratio 1:0.5~1:2) and treat it at 40-60℃ for 5-15 minutes to form a continuous gradient transition between the high concentration layer and the subsequent low concentration layer, and eliminate the interlayer interface.

[0022] S4: Low concentration touch-up coating: Immerse the resin blank after step (3) into the second concentration dip coating solution and treat it at 40-60℃ for 10-30 minutes to make the UV absorption functional components form a low concentration distribution area inside the resin blank.

[0023] S5: Complete curing: The resin preform after step (4) is completely cured (70-90℃, 2-6 hours) to obtain a resin material with a continuous gradient distribution of high concentration on the surface and low concentration in the interior of the ultraviolet absorption functional component.

[0024] Control principles of key process parameters:

[0025] Low-temperature pre-curing at 40-60℃: This temperature range keeps the resin preform in a gel state, allowing functional components to diffuse into the surface through swelling, while preventing the resin from curing too quickly and fixing the functional components due to excessively high temperatures. Below 40℃, the diffusion rate is too slow, and above 60℃, the resin curing rate is too fast, neither of which can form an effective gradient.

[0026] The three-step dipping coating sequence is as follows: a high-concentration initial coating establishes a high-concentration surface layer; a transitional coating ensures a smooth transition from high to low concentration; and a low-concentration coating ensures a low-concentration zone within the interior. This sequence ensures a continuous decrease in concentration from the surface to the interior, rather than a step-like abrupt change.

[0027] Interlayer solubility: Since each step is carried out in an incompletely cured state, intersolubility occurs between the front and rear impregnation layers, forming a continuous gradient structure without a clear interface. This is the key difference from existing multilayer coating schemes.

[0028] Composition of UV absorption functional components:

[0029] The ultraviolet absorption functional component includes the following four additives: primary antioxidant, secondary antioxidant, ultraviolet absorber, and light stabilizer, with a preferred mass ratio of 2:1:1.5:1. In addition, it may include surface-modified nanofillers (such as nano-titanium dioxide and nano-silica) to enhance the physical shielding effect. However, the core of this invention lies in the gradient distribution process; the specific formulation of the functional components can be adjusted as needed without affecting the scope of protection of the process method.

[0030] The resin preform is an incompletely cured thermosetting resin (such as polyurethane, epoxy resin, acrylic resin, etc.) molded body, with a curing degree from gel state to semi-cured state (usually after pre-curing at 30-60℃ for 20-40 minutes) so that functional components can penetrate and diffuse.

[0031] The solvent in the dip coating solution is an organic solvent that can dissolve the ultraviolet absorption functional components and has a certain swelling effect on the resin preform, such as ethyl acetate, acetone, butanone, ethanol, or mixtures thereof.

[0032] The beneficial effects of this invention are:

[0033] Achieving a continuous gradient distribution: By following a specific sequence of "high-concentration initial coating → transition treatment → low-concentration touch-up coating" and combined with low-temperature pre-curing control at 40-60℃, a continuous concentration gradient of UV absorption functional components from the surface to the interior was successfully constructed. The surface layer has a high concentration, the interior layer has a low concentration, and the layers are mutually soluble with no clear interface.

[0034] Strong UV resistance on the surface: The concentration of UV absorber in the 0-50μm area of ​​the surface layer is 3-10 times that of the internal area, which can efficiently absorb UV light entering the surface layer and protect the deep resin from damage.

[0035] High internal transparency: The content of internal ultraviolet absorbers is low, and the resin transmittance is ≥90%, which avoids the scattering and absorption of visible light by additives in the uniformly distributed scheme.

[0036] 100% Preservation of Fine Surface Texture: Due to the use of low-temperature pre-curing, the layers are mutually soluble, preventing the formation of discrete coating interfaces. The micron-level texture (5-50μm depth) on the resin surface is not filled in, completely preserving the original fineness. This is an effect that existing coating solutions cannot achieve.

[0037] Simple process and low cost: Only conventional dip coating equipment and temperature control device are required, without the need for complex equipment; the amount of functional components used is reduced by 30%-50% compared with the uniform distribution scheme, thus reducing raw material costs.

[0038] High versatility: It is suitable for a variety of thermosetting resin systems and can be applied to fine handicrafts such as BJD dolls, figurines, and art ornaments. It can also be extended to other products that require surface weather resistance and internal transparency.

[0039] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0040] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Detailed Implementation

[0041] The present invention is illustrated below with specific embodiments, which are not intended to limit the scope of the invention.

[0042] Example 1

[0043] Resin preform: A sheet sample of polyurethane resin prepolymer cast into shape, 3 mm thick, which is pre-cured at 60°C for 30 min (in a gel state).

[0044] Preparation of dipping solution:

[0045] First concentration dipping solution: Dissolve 5 parts of UV absorber UV-328 in ethyl acetate (95 parts) to obtain a solution with a solid content of 5%.

[0046] Second concentration dip coating solution: Take the first concentration dip coating solution and dilute it with ethyl acetate to a solid content of 1.5% (i.e. 30% of the first concentration).

[0047] Gradient processing:

[0048] The resin preform is immersed in the first concentration dip coating solution and treated at 50°C for 10 minutes.

[0049] Transfer to a 1:1 mixture of first and second solutions and treat at 50°C for 8 minutes.

[0050] Transfer to the second concentration of dipping solution and treat at 50°C for 15 minutes;

[0051] Remove and allow to cure completely at 80℃ for 4 hours.

[0052] Results: The UV-328 concentration in the 0-20μm area of ​​the surface is about 4.2%, and the concentration in the interior is about 0.8%, with a clear gradient; the surface texture depth retention rate is 100%; the light transmittance is 91%; after accelerated aging for 2000h, ΔE=2.5.

[0053] Example 2

[0054] Resin preform: Epoxy resin doll head preform (pre-cured at 50℃ for 40 minutes, in a semi-cured state).

[0055] Preparation of dipping solution:

[0056] First concentration dipping solution: 10 parts of quaternary additives (main antioxidant 1010: auxiliary antioxidant 168: UV-328: light stabilizer 292 = 2:1:1.5:1), 3 parts of nano TiO2 (particle size 30nm, KH570 modified), dissolved in ethyl acetate to a total solid content of 18%.

[0057] Second concentration dipping solution: Dilute the first concentration dipping solution to a solid content of 6% (33% of the first concentration).

[0058] Gradient processing:

[0059] The initial doll blank was immersed in the first concentration of the coating solution and treated at 55°C for 12 minutes.

[0060] Transfer to a mixture of first and second solutions in a ratio of 1:1.2, and treat at 55°C for 10 minutes;

[0061] Transfer to the second concentration of dipping solution and treat at 55°C for 20 minutes;

[0062] Remove and allow to cure completely at 80℃ for 5 hours.

[0063] Results: The concentration of anti-yellowing functional components in the surface 50μm area is 5 times that in the interior; the pre-set skin pore texture (depth of about 20μm) on the surface is 100% preserved without filling; light transmittance is 93%; after 2000h of accelerated aging, ΔE=1.9.

[0064] Comparative Example 1 (Uniform Blending Method)

[0065] The same quaternary additives and nanofillers were directly and uniformly mixed into the epoxy resin matrix, and then cast and cured. Results: Overall light transmittance was only 78%; under the same aging conditions, ΔE=3.5; surface texture was partially lost due to grinding.

[0066] Comparative Example 2 (conventional dip coating followed by direct curing, without gradient transition)

[0067] After a single treatment with the first concentration of dipping solution, the coating was directly and completely cured (without transition or touch-up coating). Result: A discrete coating was formed on the surface, the texture was filled in (coating coverage was visible under a microscope), and there were no functional components inside. Severe yellowing occurred after deep aging.

[0068] Comparative Example 3 (cured at a single temperature, without controlled miscibility)

[0069] The same steps as in Example 1 were used, but the low-temperature pre-curing temperature was increased to 80°C. Result: The resin preform cured rapidly, the functional components could not penetrate and diffuse, only a small amount of additives adhered to the surface, no gradient was formed, and ΔE=5.2.

[0070] Process parameter range verification

[0071] The inventors determined the preferred range of process parameters through orthogonal experiments:

[0072] Low-temperature pre-curing temperature: 40-60℃. At <40℃, the gradient forms slowly; above 60℃, the resin cures too quickly, and the gradient fails.

[0073] First concentration of solid content: 10%-25%; <10% gradient is not obvious; >25% easily forms an interface.

[0074] The ratio of the second concentration to the first concentration should be 20%-40%. If it exceeds this range, the gradient curve will not be ideal.

[0075] Transition processing time: 5-15 min; <5 min: interface not eliminated; >15 min: gradient over-homogenization;

[0076] Reapplication time: 10-30 min; <10 min: internal concentration is too low; >30 min: gradient improvement is not obvious;

[0077] Effective gradient distribution can be achieved within the above range, with 100% surface texture retention.

[0078] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0079] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

[0080] 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 of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A resin anti-aging treatment method based on ultraviolet absorption gradient distribution, characterized in that, Includes the following steps: S1: Prepare a first concentration immersion coating solution and a second concentration immersion coating solution, wherein the concentration of the ultraviolet absorption functional component in the first concentration immersion coating solution is higher than that in the second concentration immersion coating solution. S2: Immerse the uncured resin blank in the first concentration of dipping solution and pre-cur it at a low temperature of 40-60℃ for 5-20 minutes. S3: Immerse the resin preform treated with S2 into a mixture of the first concentration dipping solution and the second concentration dipping solution, and perform a transition treatment at 40-60℃ for 5-15 minutes. S4: Immerse the resin preform treated in S3 into the second concentration dip coating solution and perform a touch-up coating treatment at 40-60℃ for 10-30 minutes; S5: Complete curing yields a resin material with a gradient distribution of high concentration of UV-absorbing functional components on the surface and low concentration inside.

2. The method according to claim 1, characterized in that: The ultraviolet absorption functional components include a primary antioxidant, a secondary antioxidant, an ultraviolet absorber, and a light stabilizer, with a mass ratio of 2:1:1.5:

1.

3. The method according to claim 1, characterized in that: The solid content of the first concentration dipping solution is 10%-25%, and the solid content of the second concentration dipping solution is 20%-40% of that of the first concentration dipping solution.

4. The method according to claim 1, characterized in that: The volume ratio of the mixed solution in S3 is 1:0.5 to 1:2 for the first concentration dipping solution and the second concentration dipping solution.

5. The method according to claim 1, characterized in that: The resin preform is an incompletely cured molded body of polyurethane resin, epoxy resin, or acrylic resin.

6. The method according to claim 1, characterized in that: The ultraviolet absorption functional component also includes surface-modified nanofillers.

7. The method according to claim 1, characterized in that: The low-temperature pre-curing causes mutual solubility between the various impregnation layers, resulting in a gradient distribution that is a continuous gradient without interlayer interfaces.

8. The resin material prepared by the method according to any one of claims 1 to 7.

9. The use of the resin material according to claim 8 in the preparation of ball-jointed dolls, figurines, or fine handicrafts.

10. An apparatus for implementing the method of claim 1, characterized in that: It includes at least one dip coating tank, a temperature control device, and a curing device.