Micro-foaming light reflecting plate and preparation method thereof

Abstract

The invention discloses a micro-foaming light reflecting plate and a preparation method thereof, the micro-foaming light reflecting plate comprises a light reflecting plate body, the light reflecting plate body is made of polyethylene glycol terephthalate foam, the crystallinity of a polymer matrix of the light reflecting plate body is 30%-45%, the average cell size is smaller than 20 microns, and the light reflectivity of the light reflecting plate body is 90% or above. According to the invention, polyethylene glycol terephthalate is selected as a base material to prepare the light reflecting plate, and the foaming behavior and physical properties of the material can be regulated and controlled by controlling the crystallinity, so that the micro-foaming material with fine, dense and uniform small cells is obtained, and the polymer foam material has excellent light reflecting performance and can be used for preparing the light reflecting plate. The industrial application of the PET foaming material in the fields of liquid crystal display, semiconductor illumination and the like is widened.

Description

Technical Field

[0001] This invention relates to the field of foamed materials technology, and in particular to a micro-foamed light reflector and its preparation method. Background Technology

[0002] Light reflectors, by reflecting light, can significantly improve light utilization and are key materials in LCD TVs, tablets, mobile phone backlight modules, and semiconductor lighting. Currently, common light reflector substrates include acrylonitrile-butadiene-styrene (ABS), polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), and polyethylene terephthalate (PET), which are prepared through methods such as biaxial stretching and surface coating. However, biaxial stretching requires precise control of parameters such as temperature, speed, and stretch ratio; while surface coatings may not adhere sufficiently, leading to peeling or blistering. Furthermore, light reflectors prepared using existing technologies typically have a high density, hindering lightweight designs.

[0003] Polymer foaming technology holds promise for the fabrication of low-density, lightweight PET light reflective panels. For foamed materials, cell size directly impacts light reflectivity. However, PET's slow crystallization rate and low melt strength mean that the PET matrix cannot support continuous cell growth during foaming, leading to gas escape, cell coalescence, and even rupture. These phenomena result in excessively large and uneven cell sizes, negatively affecting the light reflectivity of the foamed material. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to develop a micro-bubble light reflector and its fabrication process, thereby achieving a lightweight design of the light reflector while ensuring excellent light reflection performance.

[0005] To achieve the above objectives, the present invention provides a micro-foamed light reflector, comprising a light reflector body, wherein the material of the light reflector body is PET foam, the crystallinity of its polymer matrix is ​​30%~45%, the average cell size is less than 20μm, and the light reflectivity of the light reflector body is above 90%.

[0006] This invention selects PET as the matrix material to prepare a light reflector. The crystallinity of PET is controllable. By controlling the crystallinity, the foaming behavior and physical properties of the material can be regulated. On the one hand, the crystal provides a large number of heterogeneous nucleation interfaces, which reduces the energy barrier for cell nucleation and thus promotes cell nucleation. On the other hand, by increasing the stiffness of the matrix, cell growth is restricted, thereby obtaining a micro-foamed material with fine and uniform small cells. This polymer foam material has excellent light reflection performance, which is conducive to broadening the industrial application of PET foam materials in fields such as liquid crystal displays and semiconductor lighting.

[0007] Furthermore, the relationship between the crystallinity of the polymer matrix of the light reflector body and the size of each pore conforms to the following formula: y = 25 / x - 50 ± 15 Where x is the crystallinity of the polymer matrix and y is the pore size in μm.

[0008] This invention controls the size of the bubbles by adjusting the crystallinity of the matrix, resulting in uniform and fine bubbles and consistent light reflection performance in all parts of the light reflector.

[0009] The present invention also provides a method for preparing the above-mentioned micro-bubble light reflector, comprising the following steps: S1. Place PET granules in a mold, press them using a flat vulcanizing machine, and then quench them to obtain sheet material. S2. Anneal the sheet material obtained in step S1. After annealing, the crystallinity of PET is 30%~45%. S3. Put the material obtained in step S2 into a high-pressure reactor and saturate it with saturated gas. S4. Transfer the material obtained in step S3 to a foaming medium for heating and foaming. S5. Transfer the material obtained in step S4 to ice water for quenching to obtain a micro-bubbled light reflector.

[0010] This invention utilizes cold crystallization technology to control the formation of a large number of fine crystal grains in PET, and prepares foamed materials with fine and uniform small pores by controlling the foaming process. This achieves a lightweight design for light reflectors, and the production process does not require the addition of additives such as chain extenders, compatibilizers, coupling agents, and bubble nucleating agents. The production process is simple, low-cost, and environmentally friendly.

[0011] Furthermore, in step S2, the annealing temperature is 100~130℃, the annealing time is 3~30min, and the annealing temperature T and time t satisfy the relationship: t=-2 / 3T+(88±10), where T is in ℃ and t is in min.

[0012] Further, in step S2, when the annealing temperature is 100~105℃, the annealing time is 22~30min; when the annealing temperature is 105~110℃, the annealing time is 14~22min; when the annealing temperature is 110~115℃, the annealing time is 12~14min; when the annealing temperature is 115~120℃, the annealing time is 9~12min; and when the annealing temperature is 120~130℃, the annealing time is 3~9min.

[0013] This invention allows for precise control of the crystallization behavior of PET by adjusting the annealing temperature and annealing time, thereby changing the crystal size and morphology of the PET material and thus regulating its foaming behavior and physical properties.

[0014] Furthermore, in step S1, the thickness of the sheet material is 0.25~2mm.

[0015] Furthermore, in step S1, the molding temperature is 270~300℃, the pressure is 5~15MPa, and the time is 5~15min.

[0016] Molding processes can be used to design PET materials to the required size, reducing subsequent processing steps.

[0017] Furthermore, in step S3, the saturated gas is carbon dioxide, the saturation pressure is 2~6 MPa, and the saturation time is 24~72 h.

[0018] Furthermore, in step S4, the foaming temperature is 90~120℃ and the foaming time is 10~30s.

[0019] Furthermore, in step S4, the foaming medium is selected from one of dimethyl silicone oil, glycerin, and vegetable oil.

[0020] By using environmentally friendly carbon dioxide as a foaming agent and controlling the foaming conditions to intermittently foam PET sheet material, a foam material with an average cell size of less than 20μm was obtained.

[0021] In summary, compared with the prior art, the present invention has the following beneficial effects: This invention uses polyethylene terephthalate as raw material and obtains a PET foam material with fine and uniform small pores by controlling the crystallinity and pore size of the polymer matrix. This material has the characteristics of low density and high light reflectivity, which is conducive to expanding the industrial application of PET foam materials in fields such as liquid crystal displays and semiconductor lighting.

[0022] This invention combines molding, cold crystallization, and high-pressure foaming technologies to effectively control the crystal structure and pore structure of the material, thereby achieving the preparation of lightweight PET micro-foamed light reflectors. The preparation process is simple, does not require the use of additives, and is environmentally friendly. Attached Figure Description

[0023] Figure 1 Scanning electron microscope image of the PET microbubble light reflector prepared in Example 2 of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the PET microbubble light reflector prepared in Example 7 of the present invention.

[0025] Figure 3 This is a scanning electron microscope image of the PET foam board prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art.

[0029] The present invention provides a micro-bubble light reflector and its preparation method, the specific steps of which are as follows: S1. Place PET granules in a mold, use a flat vulcanizing machine for molding, and then quench them to obtain sheet material.

[0030] In a specific embodiment, the size of the sheet material corresponds to the size of the mold cavity, and the thickness of the sheet material is 0.25~2mm. Preferably, the thickness of the sheet material is 1~1.5mm.

[0031] In a specific embodiment, the molding conditions are controlled according to the characteristics of PET. Generally, the molding temperature is 270~300℃, the pressure is 5~15MPa, and the time is 5~15min. Preferably, the molding temperature is 280~290℃, the pressure is 10~15MPa, and the time is 10~15min.

[0032] S2. Place the quenched sheet material into an oven for annealing to crystallize PET. The annealing temperature is 100~130℃ and the annealing time is 3~30min. The annealing temperature T (℃) and time t (min) satisfy the following relationship: t=-2 / 3T+(88±10).

[0033] Preferably, when the annealing temperature is 100~105℃, the annealing time is 22~30 min; when the annealing temperature is 105~110℃, the annealing time is 14~22 min; when the annealing temperature is 110~115℃, the annealing time is 12~14 min; when the annealing temperature is 115~120℃, the annealing time is 9~12 min; and when the annealing temperature is 120~130℃, the annealing time is 3~9 min. By precisely controlling the annealing temperature and time, the crystallization behavior of PET is regulated, ensuring that the crystallinity of PET after annealing is 30%~45%.

[0034] S3. Place the annealed sheet into a high-pressure autoclave and introduce saturated gas to saturate it.

[0035] In a specific embodiment, CO2 is selected as the saturated gas, the saturation pressure is 2~6 MPa, and the saturation time is 24~72 h. Preferably, the saturation pressure is 3~5 MPa, and the saturation time is 60~70 h.

[0036] S4. After the saturation process is completed, transfer the sample to an oil bath for heating and foaming.

[0037] In a specific embodiment, the foaming medium can be selected from dimethyl silicone oil, glycerin, vegetable oil, machine oil, etc., the foaming temperature is 90~120℃, and the foaming time is 10~30s. By controlling the foaming conditions, PET sheet material is intermittently foamed to obtain a foam material with an average cell size of less than 20μm.

[0038] S5. After foaming, the material is transferred to ice water for quenching to fix the cell structure and obtain a micro-foamed light reflector.

[0039] The above preparation method utilizes cold crystallization technology to control a large number of fine crystal grains in PET, and prepares foamed materials with fine and uniform small pores by controlling the foaming process, thus realizing the lightweight design of light reflectors. Moreover, the production process does not require the addition of additives such as chain extenders, compatibilizers, coupling agents, and bubble heterogeneous nucleating agents. The production process is simple, low-cost, and environmentally friendly.

[0040] The light reflector provided in this specific embodiment is made of PET foam, with a polymer matrix crystallinity of 30%~45% and an average cell size of less than 20μm. The cells are uniformly distributed, and the cell size satisfies the following formula: y=25 / x-50±15, where x is the polymer matrix crystallinity and y is the cell size (μm).

[0041] The aforementioned light reflector has fine and uniform small pores, achieving a lightweight design, and has a light reflectivity of over 90%, exhibiting excellent light reflection performance. This is beneficial for expanding the industrial application of PET foam materials in fields such as liquid crystal displays and semiconductor lighting.

[0042] The technical solution and effects of the present invention will be illustrated below with specific embodiments.

[0043] Example 1

[0044] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 130℃ for 5 minutes, and the polymer matrix crystallinity was measured to be 42.7%. The annealed sheet was then placed in an autoclave, CO2 was introduced, and the material was saturated at 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 110℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector.

[0045] The average pore size of the PET microbubble light reflector prepared in this embodiment was 11.4 μm, and the light reflectivity was 94.3%.

[0046] Example 2

[0047] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterwards, quenching was performed to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 118℃ for 10 minutes, and the polymer matrix crystallinity was measured to be 34.6%. The annealed sheet was then placed in an autoclave, CO2 was introduced, and the material was saturated at 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 110℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector plate. The cell structure is shown below. Figure 1 As shown.

[0048] The average pore size of the PET microbubble light reflector prepared in this embodiment was 12.2 μm, and the light reflectivity was 93.0%.

[0049] Example 3

[0050] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 118℃ for 10 minutes, and the polymer matrix crystallinity was measured to be 34.6%. The annealed sheet was then placed in an autoclave, and CO2 was introduced, saturating it at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 115℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector.

[0051] The average pore size of the PET microbubble light reflector prepared in this embodiment was 14.1 μm, and the light reflectivity was 92.3%.

[0052] Example 4

[0053] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 118℃ for 10 minutes, and the polymer matrix crystallinity was measured to be 34.6%. The annealed sheet was then placed in an autoclave, and CO2 was introduced, saturating it at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 120℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector.

[0054] The average pore size of the PET microbubble light reflector prepared in this embodiment was 15.9 μm, and the light reflectivity was 91.1%.

[0055] Example 5

[0056] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 120℃ for 10 minutes, and the polymer matrix crystallinity was measured to be 42.1%. The annealed sheet was then placed in an autoclave, and CO2 was introduced, saturating it at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 120℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector.

[0057] The average pore size of the PET micro-foamed light reflector prepared in this embodiment was 11.8 μm, and the light reflectivity was 93.5%.

[0058] Example 6

[0059] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 118℃ for 12 minutes, and the polymer matrix crystallinity was measured to be 38.3%. The annealed sheet was then placed in an autoclave, and CO2 was introduced, saturating it at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 115℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector.

[0060] The average pore size of the PET microbubble light reflector prepared in this embodiment was 12.5 μm, and the light reflectivity was 92.8%.

[0061] Example 7

[0062] PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterwards, quenching was performed to obtain PET sheet material. The quenched sheet was then placed in an oven for annealing at 114℃ for 15 minutes, and the polymer matrix crystallinity was measured to be 42.9%. The annealed sheet was then placed in an autoclave, CO2 was introduced, and the material was saturated at 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 120℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET micro-foamed light reflector plate. The cell structure is shown below. Figure 2 As shown.

[0063] The average pore size of the PET microbubble light reflector prepared in this embodiment was 10.9 μm, and the light reflectivity was 94.8%.

[0064] Comparative Example 1 PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterward, the material was quenched to obtain PET sheet material. The quenched sheet was placed in an autoclave, CO2 was introduced, and the material was saturated at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 110℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET foamed board.

[0065] The average cell size of the PET foam board prepared in this comparative test was 90.6 μm, and the light reflectance was 46.5%.

[0066] Comparative Example 2 PET granules were placed in a mold with a designed thickness of 1 mm and molded for 10 minutes using a flat vulcanizing machine at a temperature of 285℃ and a pressure of 15 MPa. Afterwards, the material was quenched to obtain PET sheet material. The quenched sheet was placed in an autoclave, CO2 was introduced, and the material was saturated at a pressure of 4 MPa for 72 hours. After saturation, the sample was transferred to a dimethyl silicone oil bath pre-set to 120℃, and the foaming time was set to 20 seconds. After foaming, the material was transferred to ice water for quenching to fix the cell structure, resulting in a PET foamed board with the following cell structure: Figure 3 As shown.

[0067] The average cell size of the PET foam board prepared in this comparative test was 78.6 μm, and the light reflectance was 55.9%.

[0068] The physical property test results of the PET foam materials obtained in Examples 1 to 7, Comparative Examples 1 and 2 are shown in Table 1 below. It can be seen that the annealed PET sheet has a suitable degree of crystallinity. Combined with a specific foaming process, a foam material with an average cell size of less than 20 μm was obtained. This micro-foamed light reflector has excellent light reflection performance with a light reflectivity of over 90%.

[0069] Table 1 Performance test results of PET foam materials in the examples and comparative examples sample Crystallinity (%) Cell size (μm) Light reflectance (%) Example 1 42.7 11.4 94.3 Example 2 34.6 12.2 93.0 Example 3 34.6 14.1 92.3 Example 4 34.6 15.9 91.1 Example 5 42.1 11.8 93.5 Example 6 38.3 12.5 92.8 Example 7 42.9 10.9 94.8 Comparative Example 1 / 90.6 46.5 Comparative Example 2 / 78.6 55.9 While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A micro-bubble light reflector, characterized in that, The light reflector body is made of polyethylene terephthalate foam, the crystallinity of its polymer matrix is ​​30%~45%, the average cell size is less than 20μm, and the light reflectivity of the light reflector body is above 90%.

2. The micro-bubble light reflector according to claim 1, characterized in that, The relationship between the average pore size of the light reflector body and the crystallinity of the polymer matrix conforms to the following formula: y = 25 / x - 50 ± 15 Where x is the crystallinity of the polymer matrix and y is the average cell size in μm.

3. A method for preparing a micro-bubble light reflector as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Place polyethylene terephthalate granules in a mold, press them using a flat vulcanizing machine, and then quench them to obtain sheet material. S2. Anneal the sheet material obtained in step S1. After annealing, the crystallinity of polyethylene terephthalate is 30%~45%. S3. Put the material obtained in step S2 into a high-pressure reactor and saturate it with saturated gas. S4. Transfer the material obtained in step S3 to a foaming medium for heating and foaming. S5. Transfer the material obtained in step S4 to ice water for quenching to obtain a micro-bubbled light reflector.

4. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S2, the annealing temperature is 100~130℃, the annealing time is 3~30min, and the annealing temperature T and time t satisfy the relationship: t=-2 / 3T+(88±10), where T is in ℃ and t is in min.

5. The method for preparing the microbubble light reflector according to claim 4, characterized in that, In step S2, when the annealing temperature is 100~105℃, the annealing time is 22~30min; when the annealing temperature is 105~110℃, the annealing time is 14~22min; when the annealing temperature is 110~115℃, the annealing time is 12~14min; when the annealing temperature is 115~120℃, the annealing time is 9~12min; and when the annealing temperature is 120~130℃, the annealing time is 3~9min.

6. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S1, the thickness of the sheet material is 0.25~2mm.

7. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S1, the molding temperature is 270~300℃, the pressure is 5~15MPa, and the time is 5~15min.

8. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S3, the saturated gas is carbon dioxide, the saturation pressure is 2~6MPa, and the saturation time is 24~72h.

9. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S4, the foaming temperature is 90~120℃ and the foaming time is 10~30s.

10. The method for preparing the microbubble light reflector according to claim 3, characterized in that, In step S4, the foaming medium is selected from one of dimethyl silicone oil, glycerin, and vegetable oil.

Images