Color-changing reflective silica gel sheet and preparation method thereof

Abstract

The invention relates to the technical field of reflective materials, and discloses a color-changing reflective silica gel sheet and a preparation method thereof.The color-changing reflective silica gel sheet comprises a reflective substrate layer, a UV color-changing functional layer and a gum bonding layer which are sequentially arranged; the reflective substrate layer is formed by mixing and vulcanizing addition type liquid silicone rubber and modified glass beads, the viscosity of the addition type liquid silicone rubber is 5000-8000 mPas (25 DEG C), the vinyl content is 0.15%-0.25%, and the shore hardness A is 30-40; the modified glass beads are mixed sand with the particle size of 10-100 microns, and are subjected to wet grinding treatment and surface activation treatment; the UV color-changing functional layer is formed by UV curing of UV curing color-changing paint coated on the surface of the reflective substrate layer, double-interface modification is carried out on the glass beads, so that the interface bonding force between the glass beads and a silica gel substrate is increased, the problem of reflective failure caused by falling of the glass beads in long-term use is avoided, and the service life of the reflective substrate layer is prolonged. Meanwhile, the particle size distribution and the adding mode of the glass beads are optimized, the light reflecting efficiency is improved, and the retroreflection coefficient is improved by 20% or above compared with the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reflective materials, in particular to a color-changing reflective silicone sheet and a preparation method thereof. BACKGROUND

[0002] Currently, reflective materials such as reflective films and PVC reflective coatings have the problems of poor color-changing flexibility and complex installation process in applications, which are difficult to meet the comprehensive needs of diversified scenes (such as traffic safety, industrial identification, and personalized decoration) for "reflective warning + color customization + convenient installation". Liquid silicone rubber (LSR) has become an ideal substrate due to its advantages of high flexibility, weather resistance (-50℃~200℃), and environmental friendliness, but its surface reflective performance needs to be enhanced by fillers, and traditional color-changing processes (such as spraying and printing) have the defects of low color fastness and complex process.

[0003] In the prior art, a reflective silicone composite material and a preparation method thereof (CN113527189A) uses glass beads for filling but does not combine with UV color-changing technology, and the color is fixed and cannot be adjusted; the preparation process of a color-changing silicone sheet (JP2021082456A) uses a dye doping method to change color, which has poor color fastness and affects the reflective performance; and it does not involve color-changing function and has insufficient adhesive force of the back adhesive. These prior arts have many shortcomings. In terms of color-changing limitations, traditional color-changing methods (dye doping and printing) have limited color types, and are prone to color fading and color difference problems. There is a contradiction between reflectivity and color-changing, and the color-changing coating covers the reflective fillers, resulting in a decrease in the retroreflective coefficient (decrease≥30%). The installation is complex, professional tools are needed to assist in pasting, and the adaptability to curved and rough surfaces is poor. The interface bonding is weak, and the interface bonding force between the glass beads and the silicone matrix is insufficient, which can easily fall off and cause reflective failure after long-term use. SUMMARY

[0004] The present application aims to provide a color-changing reflective silicone sheet and a preparation method thereof to solve the problems raised in the background.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solution: a color-changing reflective silicone sheet, comprising a reflective substrate layer, a UV color-changing functional layer, and a back adhesive bonding layer arranged in sequence; the reflective substrate layer is formed by mixing and vulcanizing addition-type liquid silicone rubber and modified glass beads, the viscosity of the addition-type liquid silicone rubber is 5000-8000 mPa・s (25℃), the vinyl content is 0.15%-0.25%, and the Shore A hardness is 30-40; the modified glass beads are mixed sand with a particle size of 10-100 μm, and are subjected to wet grinding treatment and surface activation treatment; the UV color-changing functional layer is formed by UV curing of the UV curing color-changing coating applied on the surface of the reflective substrate layer, and the coating amount is 8-12 g / m 2The adhesive backing layer is an acrylic pressure-sensitive adhesive coated on the surface of the UV color-changing functional layer, with a coating amount of 50-80 g / m². 2 .

[0006] Optionally, the modified glass microspheres contain 30% 10-30μm, 50% 30-60μm, and 20% 60-100μm; the wet milling treatment uses ethanol as the medium, a ball-to-material ratio of 5:1, and ball milling for 2 hours to reduce the glass microsphere particle size to D50=50μm; the surface activation treatment uses a 5% γ-methacryloyloxypropyltrimethoxysilane ethanol solution for ultrasonic dispersion at a frequency of 40kHz for 30 minutes, followed by vacuum drying at 80℃ for 4 hours.

[0007] A method for preparing a color-modified reflective silicone sheet includes the following steps:

[0008] Step 1: Raw material selection and pretreatment. Addition-cured liquid silicone rubber is selected as the silicone matrix, and mixed sand glass microspheres with a particle size of 10-100μm are selected. The glass microspheres are subjected to wet grinding and surface activation treatment.

[0009] Step 2: Mixing process, the silicone matrix is ​​mixed with 5 phr of dimethyl silicone oil at low speed, then modified glass microspheres are added in three parts and sheared at high speed, then 3 phr of hydrogen-containing silicone oil crosslinking agent is added and stirred, the viscosity is tested and plasticizer is added to adjust to 20000-30000 mPa·s.

[0010] Step 3: Compression molding process. The mold is pretreated by injecting the mixed material into the mold for preforming and vulcanization, followed by post-processing.

[0011] Step 4: Color change process. A UV-curable color change coating is applied to the surface of the molded silicone sheet and cured by UV curing equipment.

[0012] Step 5: Adhesive-backed lamination process. Acrylic pressure-sensitive adhesive is coated onto the surface of the color-modified silicone sheet and then laminated with release paper.

[0013] Optionally, in step 2, the low-speed mixing speed is 50-80 rpm and the time is 5 min; the high-speed shearing speed is 150-200 rpm and the time is 10 min each time, with the temperature controlled at 60-80℃; the stirring speed after adding the hydrogen-containing silicone oil crosslinking agent is 300 rpm and the time is 5 min.

[0014] Optionally, the mold pretreatment in step 3 is coating 5% dimethyl silicone oil release agent and baking at 80-100℃ for 10 min; the preforming temperature is 80℃, the time is 3-5 min, and the injection thickness is 0.5-1.0 mm; the curing treatment temperature is 150-180℃, the time is 10-15 min, the pressure is 10-15 MPa, and the curing degree is ≥95%; and the post-treatment is trimming and surface cleaning.

[0015] Optionally, the wavelength of the UV curing equipment in step 4 is 365-405 nm, the intensity is 800-1200 mW / cm 2 , and the irradiation time is 20-30 s.

[0016] Optionally, the pressure of the compounding in step 5 is 0.2-0.5 MPa; before coating the acrylic pressure-sensitive adhesive, the back of the silica gel sheet is subjected to plasma treatment at a power of 100-200 W for 3-5 min to reduce the surface energy to 30-35 mN / m.

[0017] Compared with the prior art, the present application provides an improved color reflective silica gel sheet and a preparation method thereof, which has the following beneficial effects:

[0018] 1. The improved color reflective silica gel sheet and the preparation method thereof increase the interfacial bonding force between the glass microbeads and the silica gel matrix by double-interface modification of the glass microbeads, avoid the problem of reflective failure caused by glass microbead falling off during long-term use, optimize the particle size distribution and addition method of the glass microbeads, and improve the reflective efficiency by more than 20% compared with the prior art.

[0019] 2. The improved color reflective silica gel sheet and the preparation method thereof realize rapid color conversion and flexible customization by using UV curing color-changing paint and precise UV curing process, and the color variety is rich. After adding 0.5% light stabilizer, the color difference ΔE is ≤3 after weather resistance test (65℃ / 85% humidity x 1000h), the color fastness is high, and the problems of color fading and color difference existing in traditional color-changing methods are solved. At the same time, the UV color-changing functional layer does not significantly affect the reflective performance of the reflective base layer, avoiding the contradiction between reflection and color change.

[0020] 3. The improved color reflective silica gel sheet and the preparation method thereof use acrylic pressure-sensitive adhesive for the back adhesive layer, and improve the adhesion to the pressure-sensitive adhesive by plasma treatment of the back of the silica gel sheet. The back adhesive design allows the improved color reflective silica gel sheet to be pasted without professional tool assistance, and has good adaptability to curved and rough surfaces, simplifying the installation process. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure is a flow structure schematic diagram of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0023] As shown in Figure 1 The present application provides a technical solution: a color-changing reflective silicone sheet, comprising a reflective substrate layer, a UV color-changing functional layer and a back adhesive bonding layer arranged in sequence; the reflective substrate layer is formed by mixing and vulcanizing addition type liquid silicone rubber and modified glass beads, the viscosity of the addition type liquid silicone rubber is 5000-8000 mPa・s (25℃), the vinyl content is 0.15%-0.25%, and the Shore hardness A is 30-40; the modified glass beads are mixed sand with a particle size of 10-100 μm, and are subjected to wet grinding treatment and surface activation treatment; the UV color-changing functional layer is formed by UV curing of the UV curing color-changing paint coated on the surface of the reflective substrate layer, and the coating amount is 8-12 g / m²; and the back adhesive bonding layer is acrylic pressure-sensitive adhesive coated on the surface of the UV color-changing functional layer, and the coating amount is 50-80 g / m².

[0024] In the modified glass beads, 10-30 μm accounts for 30%, 30-60 μm accounts for 50%, and 60-100 μm accounts for 20%; the wet grinding treatment is to use ethanol as a medium, the ball-to-material ratio is 5:1, and the ball milling time is 2 h, so that the particle size of the glass beads is reduced to D50=50 μm; and the surface activation treatment is to use 5% γ-methacryloxypropyltrimethoxysilane ethanol solution for ultrasonic dispersion, the ultrasonic frequency is 40 kHz, and the time is 30 min, and then vacuum drying at 80℃ for 4 h.

[0025] Embodiment 1

[0026] The present embodiment proposes a preparation method of a color-changing reflective silicone sheet, comprising the following steps:

[0027] Raw material selection and pretreatment

[0028] Silicone matrix: addition type liquid silicone rubber is selected, the viscosity is 5000 mPa・s (25℃), the vinyl content is 0.15%, and the Shore hardness A is 30. Glass beads: mixed sand with a particle size of 10-100 μm is selected, wherein 10-30 μm accounts for 30%, 30-60 μm accounts for 50%, and 60-100 μm accounts for 20%. Wet grinding treatment: ethanol is used as a medium, the ball-to-material ratio is 5:1, and the ball milling time is 2 h, so that the particle size of the glass beads is reduced to D50=50 μm.

[0029] Surface activation: glass beads were placed in 5% γ-methacryloxypropyltrimethoxysilane ethanol solution, ultrasonic dispersion for 30 min at 40 kHz, and vacuum drying at 80°C for 4 h.

[0030] Mixing process: a 50L twin-screw mixer was used; the silica gel matrix was mixed with 5 phr dimethyl silicone oil at a low speed of 50 rpm for 5 min; the modified glass beads were added in three times, 1 / 3 each time, high-speed shearing at 150 rpm for 10 min each time, and the temperature was controlled at 60°C; 3 phr hydrogen-containing silicone oil crosslinking agent was added, and stirred at 300 rpm for 5 min; the viscosity was 20000 mPa・s, which met the requirements.

[0031] Molding process: the mold was pretreated and coated with 5% dimethyl silicone oil release agent, and baked at 80°C for 10 min; the vulcanization parameters were as follows: injection thickness 0.5 mm, preforming at 80°C for 3 min; vulcanization at 150°C and 10 MPa for 10 min, with a curing degree of 95%, followed by trimming and surface cleaning.

[0032] Color changing treatment process, coating UV curing color changing paint 8g / m 2 , using UV curing equipment (wavelength 365 nm, intensity 800 mW / cm 2 ) for 20 s. Back adhesive composite process, plasma treatment (100 W, 3 min) was performed on the back of the silica gel sheet, and the surface energy was reduced to 30 mN / m; coating 50g / m 2 acrylic pressure-sensitive adhesive, and composite with release paper under a pressure of 0.2 MPa.

[0033] Example 2

[0034] The present embodiment proposes a preparation method of a color-changing reflective silica gel sheet, comprising the following steps:

[0035] Raw material selection and pretreatment: silica gel matrix, addition type liquid silicone rubber, viscosity 6500 mPa・s (25°C), vinyl content 0.20%, Shore A hardness 35. Glass beads, particle size 10-100 μm mixed sand (10-30 μm accounts for 30%, 30-60 μm accounts for 50%, 60-100 μm accounts for 20%).

[0036] Modification process: same as example 1, the particle size of the treated glass beads is D50=50 μm.

[0037] Mixing process, equipment: 50L twin-screw mixer; silica gel matrix + 5 phr dimethyl silicone oil, low speed mixing at 70 rpm for 5 min; modified glass beads were added in three times, high-speed shearing at 175 rpm for 10 min each time, and the temperature was controlled at 70°C; 3 phr hydrogen-containing silicone oil crosslinking agent was added, and stirred at 300 rpm for 5 min; the viscosity was 25000 mPa・s, which met the requirements.

[0038] Coated with 5% dimethyl silicone oil release agent, baked at 90°C for 10 min. Injection thickness 0.7 mm, preformed at 80°C for 4 min; cured at 165°C, 12 MPa for 12 min, degree of cure 96%. Then trimmed and surface cleaned. Coated with UV curing color-changing paint 10 g / m 2 , UV curing equipment (wavelength 385 nm, intensity 1000 mW / cm 2 ) irradiation for 25 s. The back of the silicone sheet was plasma treated (150 W, 4 min), and the surface energy was 32 mN / m; coated with 65 g / m 2 acrylic pressure-sensitive adhesive, and compounded with release paper at 0.3 MPa.

[0039] Example 3

[0040] This example proposes a preparation method of a color-changing reflective silicone sheet, comprising the following steps:

[0041] Silicone base, addition type liquid silicone rubber, viscosity 8000 mPa・s (25°C), vinyl content 0.25%, Shore A hardness 40.

[0042] Glass beads, same as in Example 1, modified particle size D50=50 μm.

[0043] The equipment is a 50L twin-screw mixer; the silicone base + 5 phr dimethyl silicone oil is mixed at low speed of 80 rpm for 5 min; the modified glass beads are added in three times, high-speed shearing at 200 rpm for 10 min each time, temperature control at 80°C; 3 phr hydrogen-containing silicone oil crosslinking agent is added, stirring at 300 rpm for 5 min; the viscosity is 30000 mPa・s, meeting the requirements.

[0044] Mold pretreatment, coated with 5% dimethyl silicone oil release agent, baked at 100°C for 10 min. Curing parameters, injection thickness 1.0 mm, preformed at 80°C for 5 min; cured at 180°C, 15 MPa for 15 min, degree of cure 97%. Then trimmed and surface cleaned.

[0045] Coated with UV curing color-changing paint 12 g / m 2 , UV curing equipment (wavelength 405 nm, intensity 1200 mW / cm 2 ) irradiation for 30 s. The back of the silicone sheet was plasma treated (200 W, 5 min), and the surface energy was 35 mN / m; coated with 80 g / m 2 acrylic pressure-sensitive adhesive, and compounded with release paper at 0.5 MPa.

[0046] The color-changing reflective silicone sheet prepared in the above examples was tested for performance, and the results are shown in the following table:

[0047] Performance index Example 1 Example 2 Example 3 Coefficient of retroreflection (cd lx"1m"2) 350 365 370 Color difference ΔE of weather resistance test 2.5 2.2 2.0 Adhesive strength of back adhesive (N / cm) 3

[0048] The present application increases the interface bonding force of glass microbeads with silica gel matrix by double-interface modification of glass microbeads, avoids the problem of light reflection failure caused by glass microbead falling off during long-term use, optimizes the particle size distribution and adding method of glass microbeads, improves the light reflection efficiency, and the retroreflective coefficient is improved by more than 20% compared with the prior art; meanwhile, the rapid conversion and flexible customization of color are realized by using UV curing color-changing paint and precise UV curing process, and the color variety is rich. After adding 0.5% light stabilizer, the color difference ΔE is less than or equal to 3 after weather resistance test (65℃ / 85% humidity x 1000h), the color fastness is high, and the problems of fading and color difference existing in the traditional color-changing method are solved. At the same time, the UV color-changing functional layer does not have obvious influence on the light reflection performance of the light reflection base layer, avoiding the contradiction between light reflection and color-changing.

[0049] The foregoing has described the present application in detail, but some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, the modifications or improvements without departing from the spirit of the present application are within the protection scope of the present application.

Claims

1. A color-changing retroreflective silicone sheeting, characterized by, The reflective base layer, the UV color-changing functional layer and the back adhesive layer are sequentially arranged; the reflective base layer is vulcanized by mixing addition type liquid silicone rubber and modified glass microbeads, the viscosity of the addition type liquid silicone rubber is 5000-8000 mPa・s (25℃), the vinyl content is 0.15%-0.25%, and the Shore hardness A is 30-40; the modified glass microbeads are mixed sand with a particle size of 10-100 μm, and are subjected to wet grinding treatment and surface activation treatment; the UV color-changing functional layer is formed by UV curing of the UV curing color-changing paint coated on the surface of the reflective base layer, and the coating amount is 8-12 g / m 2 ; and the back adhesive layer is the acrylic pressure-sensitive adhesive coated on the surface of the UV color-changing functional layer, and the coating amount is 50-80 g / m 2 .

2. The colored retroreflective sheeting of claim 1 wherein, The 10-30 μm accounts for 30%, the 30-60 μm accounts for 50%, and the 60-100 μm accounts for 20% in the modified glass microbeads; the wet grinding treatment is to reduce the particle size of the glass microbeads to D50=50 μm by using ethanol as a medium, a ball-to-material ratio of 5:1, and ball milling for 2 h; and the surface activation treatment is to use 5% γ-methacryloxypropyltrimethoxysilane ethanol solution for ultrasonic dispersion, an ultrasonic frequency of 40 kHz, and a time of 30 min, followed by vacuum drying at 80 ℃ for 4 h.

3. A method for preparing a color-changing retroreflective silicone sheet, characterized by, The method comprises the following steps: Step 1: raw material selection and pretreatment, selecting addition type liquid silicone rubber as a silicone base, selecting mixed sand glass microbeads with a particle size of 10-100 μm, and wet grinding and surface activation treatment of the glass microbeads; Step 2: mixing process, low-speed mixing of the silicone base and 5 phr dimethyl silicone oil, followed by high-speed shearing of the modified glass microbeads in three times, and then stirring of 3 phr hydrogen-containing silicone oil crosslinking agent, detection of viscosity, and supplement of plasticizer to adjust to 20,000-30,000 mPa・s; Step 3: mold pressing forming process, pretreatment of a mold, injection of the mixed material into the mold, preforming and vulcanization treatment, and then post-treatment; Step 4: color changing treatment process, coating of UV curing color changing paint on the surface of the formed silicone sheet, and irradiation and curing by using a UV curing device; Step 5: back adhesive composite process, coating of acrylic pressure-sensitive adhesive on the surface of the color changed silicone sheet, and composite with release paper.

4. The method for preparing a color-modified reflective silicone sheet according to claim 3, characterized in that, The rotation speed of the low-speed mixing in Step 2 is 50-80 rpm, and the time is 5 min; the rotation speed of the high-speed shearing is 150-200 rpm, and the time is 10 min each time, with a temperature control of 60-80 ℃; and the stirring rotation speed after adding the hydrogen-containing silicone oil crosslinking agent is 300 rpm, and the time is 5 min.

5. The method for preparing a color-modified reflective silicone sheet according to claim 3, characterized in that, The mold pretreatment in Step 3 is coating of 5% dimethyl silicone oil release agent and baking at 80-100 ℃ for 10 min; the preforming temperature is 80 ℃, the time is 3-5 min, and the injection thickness is 0.5-1.0 mm; the vulcanization treatment temperature is 150-180 ℃, the time is 10-15 min, the pressure is 10-15 MPa, and the curing degree is ≥95%; and the post-treatment is edge trimming and surface cleaning.

6. The method for preparing a color-modified reflective silicone sheet according to claim 3, characterized in that, The wavelength of the UV curing equipment described in Step 4 is 365-405 nm, the intensity is 800-1200 mW / cm 2 , and the irradiation time is 20-30 s.

7. The method for preparing a color-modified reflective silicone sheet according to claim 3, characterized in that, The composite pressure in Step 5 is 0.2-0.5 MPa; before coating of the acrylic pressure-sensitive adhesive, the back surface of the silicone sheet is subjected to plasma treatment, with a power of 100-200 W and a time of 3-5 min, so that the surface energy is reduced to 30-35 mN / m.

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