A yellowing-resistant resin composite material and its preparation method

Abstract

This invention relates to the field of polymer materials technology, specifically to an anti-yellowing resin composite material and its preparation method. It includes a resin matrix and an anti-yellowing functional system dispersed therein, characterized in that: the anti-yellowing functional system exhibits a gradient distribution structure of "high concentration on the surface and low concentration in the interior" within the resin composite material; the anti-yellowing functional system is synergistically composed of the following three parts: a resin structure-modifying component, a quaternary auxiliary agent compound system, and a surface-modified nanofiller. The gradient distribution achieves high transparency: the functional components exhibit a "high concentration on the surface and low concentration in the interior" distribution, with the concentration of ultraviolet absorber in the 0-50μm region of the surface being 3-10 times that of the interior, efficiently absorbing ultraviolet light; the interior maintains high transparency, with a light transmittance ≥92%. 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, and the micron-level texture (5-50μm depth) on the resin surface is not filled, completely preserving the original fineness.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an anti-yellowing resin composite material and its preparation method. Background Technology

[0002] Ball-jointed dolls (BJDs) and other fine crafts require extremely high standards for the transparency, texture, hardness, and color stability of the resin material over long-term use. Traditional resin materials are prone to oxidation and yellowing under prolonged exposure to light and oxygen. The main reasons include: ultraviolet rays in sunlight causing the resin molecular chains to break and generate chromophores; and oxygen participating in the oxidation reaction, accelerating the discoloration. Frequent maintenance affects the collecting experience and also limits the product's lifespan.

[0003] Currently, the main methods used in the industry to improve anti-yellowing properties include adding antioxidants or ultraviolet absorbers, and introducing anti-yellowing groups through polymerization. In existing technologies:

[0004] Patent CN119431892A discloses a PPE composite material that improves yellowing resistance by adding antioxidants, benzoin and inorganic pigments. However, this solution is mainly for electronic and electrical housings, with no requirements for transparency and surface texture, and adopts a uniform blending method.

[0005] Patent CN116478504A discloses a high-transparency, yellowing-resistant epoxy resin composite material. By dispersing the yellowing-resistant additive in the epoxy resin system, the functional components are uniformly distributed, which causes the internal additives to have an unnecessary impact on the transparency.

[0006] The patent “A potent anti-yellowing composition and its preparation method” discloses a wide range of proportions of 6-60 parts of hindered phenolic antioxidant, 10-50 parts of phosphite antioxidant, 25-65 parts of ultraviolet absorber, and 5-45 parts of hindered amine light stabilizer, but does not provide a precise optimized ratio and does not involve a gradient distribution structure.

[0007] The patent "A high refractive index, high toughness, and yellowing-resistant epoxy resin composite material" uses a blend of nanofillers, antioxidants, and ultraviolet absorbers. However, the functional components are evenly distributed, and the internal ultraviolet absorbers cause scattering loss to the transparency.

[0008] However, existing technologies share the following common drawbacks:

[0009] Waste of function: By using a blending method to uniformly disperse functional components throughout the resin matrix, the UV absorbers in the internal regions contribute almost nothing to the UV protection of the surface layer, resulting in increased costs.

[0010] 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 solutions typically achieve light transmittance below 80% when the amount added is high.

[0011] 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.

[0012] Lack of systematic synergistic design: Most solutions adopt binary modification of "main inhibitor + auxiliary inhibitor" or simple multi-component blending, lacking systematic synergy from the three levels of source yellowing suppression, process yellowing prevention and physical shielding.

[0013] Not suitable for products with high-precision surface textures: Existing technologies are mostly used in LED packaging, electronic appliance housings, and other fields where the requirements for surface texture precision are not high. BJD dolls have micron-level skin textures (depth 5-50μm), and existing coating or blending solutions cannot retain 100% of these textures while ensuring anti-yellowing.

[0014] Therefore, there is a need to develop a resin composite material that can balance anti-yellowing performance and transparent texture, while being suitable for industrial production and retaining fine surface texture. Summary of the Invention

[0015] This invention aims to resolve the contradiction between the anti-yellowing performance and transparency and surface texture retention of existing resin materials, and provides a resin composite material with a gradient anti-yellowing functional distribution and its preparation method, which achieves triple synergistic protection of source yellowing suppression, process yellowing prevention and physical shielding, while ensuring high internal transparency and 100% retention of surface texture.

[0016] Technical solution

[0017] The present invention adopts the following technical solution:

[0018] An anti-yellowing resin composite material and its preparation method are disclosed, comprising a resin matrix and an anti-yellowing functional system dispersed therein, characterized in that: the anti-yellowing functional system exhibits a gradient distribution structure of "high concentration on the surface and low concentration in the interior" in the resin composite material; the anti-yellowing functional system is composed of the following three synergistic components:

[0019] Resin structure modification components: By selecting resin monomers or prepolymers containing anti-yellowing groups, the source of yellowing reaction is inhibited at the molecular level.

[0020] The quaternary additive compound system is compounded in the following mass ratio: main antioxidant: auxiliary antioxidant: ultraviolet absorber: light stabilizer = 2:1:1.5:1, and is used to block the yellowing reaction during the resin aging process.

[0021] Surface-modified nanofillers: Surface-modified inorganic nanoparticles with silane coupling agents are used to form a UV shielding layer at the physical level, while enhancing the interfacial bonding between the nanofillers and the resin matrix.

[0022] The resin matrix is ​​selected from one or more combinations of polyurethane resin, epoxy resin, or acrylic resin. The primary antioxidant is a hindered phenolic antioxidant (preferably antioxidant 1010), the secondary antioxidant is a phosphite antioxidant (preferably antioxidant 168), the ultraviolet absorber is a benzotriazole (preferably UV-328) or triazine, and the light stabilizer is a hindered amine (preferably HALS-292). The nanofiller is selected from nano-silica, nano-titanium dioxide, or nano-zinc oxide, with a particle size of 10-100 nm, and is surface-modified with a silane coupling agent, with an addition amount of 3-8% of the resin matrix weight.

[0023] The preparation method of the above-mentioned anti-yellowing resin composite material adopts an ultraviolet absorption gradient distribution process, including the following steps:

[0024] Preparation of gradient dip coating solution:

[0025] Preparation of the first concentration dipping solution (high concentration solution): Disperse the quaternary auxiliary agent compound system and surface modified nanofiller in an organic solvent according to the formula ratio, with a solid content of 10%-25%;

[0026] Prepare the second concentration dipping solution (low concentration solution): Dilute the first concentration dipping solution to a solid content of 20%-40% of the first concentration;

[0027] 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.

[0028] Gradient transition treatment: Immerse the resin preform after step 2 into a mixture of first concentration dip coating solution and second concentration dip coating solution (volume ratio 1:0.5~1:2) and treat at 40-60℃ for 5-15 minutes to form a continuous gradient transition between the high concentration layer and the subsequent low concentration layer, eliminating the interlayer interface.

[0029] Low-concentration touch-up coating: Immerse the resin preform after step 3 into the second concentration coating solution and treat it at 40-60℃ for 10-30 minutes to form a low-concentration distribution area of ​​UV absorption functional components inside the resin preform.

[0030] Complete curing: The resin preform after step 4 is completely cured (usually at 70-90℃ for 2-6 hours) to obtain a resin composite material in which the ultraviolet absorption functional components are distributed in a gradient of high concentration on the surface and low concentration in the interior.

[0031] Key process parameter control:

[0032] Low-temperature pre-curing temperature is controlled at 40-60℃: if the temperature is too low, the functional components cannot effectively penetrate and diffuse; if the temperature is too high, the resin preform will cure rapidly, and the functional components will be fixed and unable to form a gradient.

[0033] The first concentration of the dipping solution has a solid content of 10%-25%: below 10%, the gradient is not obvious, and above 25%, an interface is easily formed.

[0034] Transition processing time is 5-15 minutes: if the time is too short, a continuous gradient cannot be formed; if the time is too long, the gradient will be over-averaged.

[0035] Beneficial effects

[0036] Triple synergistic anti-yellowing: Through the synergistic effect of resin structure modification (source suppression of yellowing), quaternary additive compounding (process yellowing inhibition), and nanofiller surface modification (physical shielding), under accelerated aging test conditions (xenon lamp 2000h), the yellowing index ΔE≤2.3, and the anti-yellowing performance is more than 3 times better than that of conventional resin.

[0037] Gradient distribution achieves high transparency: the functional components are distributed with "high concentration on the surface and low concentration in the interior". The concentration of ultraviolet absorber in the 0-50μm region on the surface is 3-10 times that in the interior, which can efficiently absorb ultraviolet light; the interior maintains high transparency with a light transmittance of ≥92%.

[0038] 100% Preservation of Fine Surface Texture: Due to the use of low-temperature pre-curing, the layers are mutually soluble and no discrete coating interface is formed. The micron-level texture (5-50μm depth) on the resin surface is not filled in, and the original fineness is completely preserved.

[0039] Cost reduction: The total amount of functional components used is reduced by 30%-50% compared to the uniform distribution scheme, and the raw material cost is reduced by 10%-24% compared to the existing technology.

[0040] The process is simple: it only requires conventional dip coating equipment and temperature control devices, making it suitable for industrial production.

[0041] 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.

[0042] 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

[0043] The present invention is illustrated below with specific embodiments, which are not intended to limit the scope of the invention.

[0044] Example 1

[0045] Material formulation: 100 parts by weight of polyurethane resin; quaternary additives: 2 parts of main antioxidant 1010, 1 part of auxiliary antioxidant 168, 1.5 parts of ultraviolet absorber UV-328, 1 part of light stabilizer HALS-292; 5 parts of nano silica (particle size 30nm, surface modified with KH570 silane coupling agent).

[0046] Preparation method:

[0047] The quaternary additives and nano-silica were dispersed in ethyl acetate to prepare a first concentration dip coating solution with a solid content of 18%; the first concentration dip coating solution was taken and diluted with ethyl acetate to a solid content of 6% to obtain a second concentration dip coating solution.

[0048] The doll head blank (pre-cured at 60℃ for 30 min, in a gel state) cast from polyurethane resin prepolymer was immersed in the first concentration dipping solution and pre-cured at 50℃ for 10 min.

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

[0050] Transfer to the second concentration of dipping solution and apply a second coat at 50°C for 15 minutes.

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

[0052] Performance testing: After 2000 hours of accelerated aging, ΔE=2.1, light transmittance 93%, surface texture depth retention rate 100%, and hardness 95D.

[0053] Example 2

[0054] The results were essentially the same as in Example 1, except that: the resin matrix was epoxy resin; the nanofiller was nano-titanium dioxide (particle size 50nm), added in 3 parts; and the low-temperature pre-curing temperature was 45℃. Test results: ΔE=2.3, light transmittance 91%, hardness 92D, texture retention 100%.

[0055] Comparative Example 1 (Conventional Resin)

[0056] Ordinary polyurethane resin, without any anti-yellowing treatment. ΔE=8.5, light transmittance 65%, micro-cracks appear on the surface, texture retention rate 80% (due to sanding loss).

[0057] Comparative Example 2 (Uniform Blending)

[0058] The formulation is the same as in Example 1, but the functional components are uniformly dispersed in the resin using a conventional blending method without gradient processing. ΔE=4.2, light transmittance 78%, texture retention 85% (due to surface effects caused by additive precipitation), hardness 88D.

[0059] Comparative Example 3 (Single Concentration Dip Coating)

[0060] Same formulation as Example 1, but treated only once with the first concentration of dip coating solution and then directly cured completely (no transition, no touch-up coating). Results: A discrete coating was formed on the surface, the texture was filled (retention rate <60%), ΔE=3.0, and the light transmittance was 80%.

[0061] 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.

[0062] 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.

[0063] 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. An anti-yellowing resin composite material and its preparation method, characterized in that, The invention comprises a resin matrix and an anti-yellowing functional system dispersed therein, characterized in that: the anti-yellowing functional system exhibits a gradient distribution structure in the resin composite material with a high concentration on the surface and a low concentration in the interior; the anti-yellowing functional system comprises a resin structure-modifying component, a quaternary additive compound system, and a surface-modified nanofiller, wherein the mass ratio of the primary antioxidant, secondary antioxidant, ultraviolet absorber, and light stabilizer in the quaternary additive compound system is 2:1:1.5:

1.

2. The anti-yellowing resin composite material according to claim 1, characterized in that: The resin matrix is ​​one or more of polyurethane resin, epoxy resin, or acrylic resin.

3. The anti-yellowing resin composite material according to claim 1, characterized in that: The primary antioxidant is a hindered phenolic antioxidant, the secondary antioxidant is a phosphite antioxidant, the ultraviolet absorber is a benzotriazole or triazine, and the light stabilizer is a hindered amine.

4. The anti-yellowing resin composite material according to claim 1, characterized in that: The nanofiller is selected from nano-silica, nano-titanium dioxide or nano-zinc oxide, with a particle size of 10-100nm, and is surface modified by silane coupling agent.

5. The anti-yellowing resin composite material according to claim 1, characterized in that: The concentration of the anti-yellowing functional component in the 0-50μm region of the surface layer is 3-10 times that in the internal region.

6. A method for preparing the anti-yellowing resin composite material according to any one of claims 1 to 5, 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 anti-yellowing 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 in 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 an anti-yellowing resin composite material.

7. The preparation method according to claim 6, 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.

8. The preparation method according to claim 6, 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.

9. The preparation method according to claim 6, characterized in that: The resin preform is an incompletely cured molded body of polyurethane resin, epoxy resin, or acrylic resin.

10. The use of the anti-yellowing resin composite material according to any one of claims 1 to 5 or the resin material prepared by the preparation method according to any one of claims 6 to 9 in the preparation of ball-jointed dolls, figurines or fine handicrafts.