Yellowing-resistant polycarbonate material with low thermal expansion coefficient as well as preparation method and application of yellowing-resistant polycarbonate material

Abstract

The invention relates to a yellowing-resistant polycarbonate material with a low thermal expansion coefficient as well as a preparation method and application of the yellowing-resistant polycarbonate material. The yellowing-resistant polycarbonate material comprises the following components in parts by mass: 80-100 parts of polycarbonate; 10 to 15 parts of modified titanium dioxide; 3-6 parts of precipitated barium sulfate; 2-8 parts of a toughening agent; 1-2 parts of an ethylene-methyl acrylate copolymer; 0.3 to 0.5 part of a lubricant; 0.3 to 0.6 part of an antioxidant; 0.1 to 0.5 part of an anti-dripping agent; 0.3 to 0.7 part of silica powder; and 0.05 to 0.15 part of a flame retardant. The preparation method comprises the following steps: adding the above components into a twin-screw extruder, and carrying out extrusion and granulation to obtain the yellowing-resistant low-thermal expansion coefficient polycarbonate material. The material is used for preparing a display back frame component and a display frame component. The anti-yellowing composite material has the advantages of excellent anti-yellowing performance, good mechanical properties, low thermal expansion coefficient and good shading performance, and meets the application requirements of display back frame components and display frame components.

Description

Technical Field

[0001] The present invention relates to the technical field of polycarbonate materials, in particular to a yellowing-resistant and low thermal expansion coefficient polycarbonate material, a preparation method and an application thereof. Background Art

[0002] Polycarbonate (PC) is a colorless, odorless, non-toxic thermoplastic engineering plastic with excellent overall performance. It is one of the five major engineering plastics and has excellent impact toughness, creep resistance, weather resistance, and self-extinguishing properties. However, PC easily decomposes under the influence of light, heat, oxygen, etc. to produce carbonyl groups. Carbonyl groups are chromogenic groups that cause PC to turn yellow, ultimately affecting the appearance of the product. In addition, the large number of ester bonds in PC molecules makes PC particularly sensitive to temperature, moisture, and shear forces. Therefore, PC is prone to degradation in hot and humid environments or during the extrusion granulation process, which can cause PC products to yellow and have reduced mechanical properties.

[0003] Chinese patent CN 116426105 A discloses a yellowing-resistant polycarbonate composite material, its preparation method, and its application. The yellowing-resistant polycarbonate composite material comprises the following components by weight: 65% to 94.5% aromatic polycarbonate; 5% to 30% coated modified titanium dioxide; 0.1% to 0.5% antioxidant; 0.2% to 2% ultraviolet absorber; and 0.05% to 3% coupling agent. The coated modified titanium dioxide comprises, from the inside out, an aluminum-doped titanium dioxide core, a silicon dioxide coating, an aluminum oxide coating, and a polyorganosiloxane coating. While this yellowing-resistant polycarbonate composite material effectively addresses the issues of yellowing and mechanical degradation of polycarbonate, it has high light transmittance and is therefore only suitable for the manufacture of light-transmitting components.

[0004] In addition to yellowing resistance, display back and frame components also require high light-shielding properties. Because they connect to the display screen, these components require a low thermal expansion coefficient to prevent damage to the display screen caused by significant dimensional changes in the polycarbonate material due to ambient temperature fluctuations.

[0005] Therefore, it is necessary to develop a polycarbonate material that has both yellowing resistance and low thermal expansion coefficient. Summary of the Invention

[0006] Based on this, it is necessary to provide a yellowing-resistant, low thermal expansion coefficient polycarbonate material, a preparation method and an application thereof to address the problems of the current polycarbonate material being prone to yellowing, mechanical degradation and high thermal expansion coefficient.

[0007] A yellowing-resistant, low thermal expansion coefficient polycarbonate material comprising the following mass components

[0008]

[0009] As a preferred solution, the polycarbonate is bisphenol A polycarbonate with a melt index of 14 to 15 g / 10 min, and the melt index test conditions are 300° C. / 1.2 kg.

[0010] As a preferred embodiment, the polycarbonate is a mixture of bisphenol A polycarbonate with a melt index of 10 g / 10 min and bisphenol A polycarbonate with a melt index of 20 g / 10 min in a mass ratio of 1:1. This effectively prevents the polycarbonate material from cooling and setting too quickly during injection molding, thereby effectively improving production quality.

[0011] As a preferred solution, the modified titanium dioxide has a rutile titanium dioxide core, and the core is provided with a zinc oxide coating layer, a silicon dioxide coating layer and a triethoxyoctylsilane coating layer in sequence from the inside to the outside.

[0012] Rutile titanium dioxide is one of the most stable crystalline forms of titanium dioxide and has a lower thermal expansion coefficient than anatase titanium dioxide. The zinc oxide coating can further enhance the UV resistance and antibacterial properties of polycarbonate, while also reducing its thermal expansion coefficient. The silica coating effectively prevents aggregation between titanium dioxide particles, further improving the stability of polycarbonate while also effectively enhancing its UV resistance. The triethoxycaprylylsilane coating effectively improves the compatibility of titanium dioxide and significantly enhances the weathering, chemical, and water resistance of polycarbonate. It also reduces friction between polycarbonate molecular chains and increases their fluidity, making them easier to form during processing, reducing energy consumption, and improving production efficiency. This helps produce components with more accurate dimensions and better surface quality.

[0013] As a preferred embodiment, the preparation method of the modified titanium dioxide comprises the following steps:

[0014] S1. Dispersing nano-rutile titanium dioxide in deionized water to obtain titanium dioxide colloids, aging them with zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9 for 5 hours, filtering and washing, and performing azeotropic distillation with n-butanol. After vacuum drying and low-temperature heat treatment, zinc oxide-coated titanium dioxide is obtained;

[0015] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; adding ethyl orthosilicate dropwise to the suspension under constant temperature and stirring for 3 hours, during which the pH value is maintained between 10-11 using a sodium hydroxide solution; after centrifugation, removing the supernatant, washing with deionized water and anhydrous ethanol, filtering, and vacuum drying to obtain composite particles;

[0016] S3. Ultrasonic dispersion of the composite particles prepared in S2 in anhydrous ethanol, addition of triethoxyoctylsilane, and adjustment of the pH to 5.5 with glacial acetic acid. Stirring and reacting at room temperature. Centrifugation and filtration, washing with ethanol, and drying to obtain modified titanium dioxide.

[0017] As a preferred solution, the mass of the zinc sulfate is 3% to 10% of the mass of the rutile titanium dioxide.

[0018] As a preferred solution, the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide. In this way, the thickness of the zinc oxide coating can reach 2-3nm, which can effectively enhance the UV resistance of polycarbonate and reduce the thermal expansion coefficient of polycarbonate by more than 10%.

[0019] As a preferred solution, the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1. 2+ Complete precipitation to form a dense zinc oxide coating.

[0020] As a preferred embodiment, the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21. This ensures that the thickness of the silicon dioxide coating reaches 1 nm. This, in conjunction with the zinc oxide coating, further enhances the polycarbonate's UV resistance, reduces the polycarbonate's thermal expansion coefficient by more than 20%, and imparts excellent mechanical properties and light-shielding properties.

[0021] As a preferred embodiment, the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0022] As a preferred solution, the mass of the triethoxyoctylsilane is 1%-3% of the mass of the composite particles.

[0023] As a preferred solution, the mass of the triethoxyoctylsilane is 1%-1.5% of the mass of the composite particles, which can effectively improve the hydrophobicity of the modified titanium dioxide and improve the compatibility between the modified titanium dioxide and polycarbonate.

[0024] As a preferred embodiment, the toughening agent is a mixture of toughening agents S-2001 and EXL-2620. S-2001, manufactured by Mitsubishi Rayon Co., Ltd. of Japan, effectively improves the stress cracking resistance and flame retardancy of polycarbonate. EXL-2620, manufactured by Rohm and Haas Company of the United States, effectively improves the notch sensitivity and thick-wall brittleness of polycarbonate, while also increasing its toughness and reducing the likelihood of surface flow marks.

[0025] As a preferred solution, the mass ratio of the toughening agent S-2001 to the toughening agent EXL-2620 is 1:3. In fact, the inventors found that the more toughening agent S-2001, the better. If too much toughening agent S-2001 is added, it will reduce the hardness of the polycarbonate, making it too soft and prone to deformation, affecting the overall structural stability and appearance quality of the product; the same is true for the toughening agent EXL-2620. The more the better. If too much toughening agent EXL-2620 is added, the hardness, rigidity and elastic modulus of the polycarbonate will be reduced, which can easily lead to flow marks, spots or other visual defects on the surface of the product. After repeated experiments, the inventors found that when the mass ratio of the toughening agent S-2001 to the toughening agent EXL-2620 is 1:3, it can effectively reduce the internal stress of the polycarbonate, effectively improve the toughness of the polycarbonate, improve the mechanical properties of the polycarbonate, and at the same time reduce the probability of surface flow marks, which helps to obtain parts with better surface quality and improve processing quality.

[0026] As a preferred solution, the lubricant is pentaerythritol stearate, which can improve the thermal stability of polycarbonate on the one hand and make the parts more easily demoulded during processing on the other hand.

[0027] As a preferred embodiment, the antioxidant is tris(2,4-di-tert-butylphenyl)phosphite or β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0028] As a preferred solution, the anti-dripping agent is polytetrafluoroethylene, acrylic acid-coated modified polytetrafluoroethylene or acrylonitrile-styrene-coated modified polytetrafluoroethylene.

[0029] As a preferred embodiment, the flame retardant is potassium perfluorobutanesulfonate.

[0030] The addition of precipitated barium sulfate can effectively improve the density, hardness, and wear resistance of polycarbonate. Ethylene-methyl acrylate copolymer can improve the compatibility between precipitated barium sulfate and modified titanium dioxide and polycarbonate, while also working synergistically with toughening agents to enhance the toughness of polycarbonate. Lubricants can effectively reduce melt viscosity and improve processing fluidity, while preventing filler (precipitated barium sulfate and modified titanium dioxide) agglomeration and promoting dispersion. Silicone powder can work synergistically with flame retardants to enhance the flame retardant efficiency of polycarbonate, while also working synergistically with lubricants to improve the melt fluidity of polycarbonate and enhance the surface smoothness, wear resistance, and scratch resistance of polycarbonate.

[0031] A method for preparing the yellowing-resistant, low thermal expansion coefficient polycarbonate material as described above comprises the following steps: adding polycarbonate, modified titanium dioxide, precipitated barium sulfate, a toughening agent, ethylene-methyl acrylate copolymer, a lubricant, an antioxidant, an anti-dripping agent, and silicone powder into a twin-screw extruder, and performing extrusion and granulation to obtain the yellowing-resistant, low thermal expansion coefficient polycarbonate material.

[0032] The specific steps are as follows:

[0033] 1. Weigh polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder in proportion, pour them into the mixing barrel, stir the materials for 10 minutes in advance, then open the discharge port and put the mixed materials into the feed barrel of the twin-screw extruder;

[0034] 2. Turn on the power of the twin-screw extruder and set the temperature of each section of the twin-screw extruder. The temperature of the first zone is set to 250℃, the temperature of the second zone is set to 260℃, the temperature of the third zone is set to 270℃, the temperature of the fourth zone is set to 270℃, the temperature of the fifth zone is set to 270℃, the temperature of the sixth zone is set to 275℃, the temperature of the seventh zone is set to 275℃, the temperature of the eighth zone is set to 280℃, the temperature of the ninth zone is set to 290℃, and the temperature of the die head is set to 300℃.

[0035] 3. After the temperature of each section of the twin-screw extruder reaches the set value, the speed of the twin-screw extruder is adjusted to between 350-400r / min, and the speed of the feeder is adjusted to between 20-30r / min. After extrusion, passing through a water trough, pelletizing, and screening, the yellowing-resistant and low thermal expansion coefficient polycarbonate material is obtained.

[0036] A use of the yellowing-resistant, low thermal expansion coefficient polycarbonate material described above in the preparation of display frame and back frame components.

[0037] The polycarbonate material of the present invention has excellent yellowing resistance, good mechanical properties, low thermal expansion coefficient, good melt fluidity, and is easy to process. Using the polycarbonate material of the present invention for processing, it is easier to obtain components with better surface quality, which can effectively improve the yield of high-quality products. The polycarbonate material of the present invention has strong insulation and good light-shielding properties, and meets the application requirements of display frame and back frame components. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a physical picture of the yellowing-resistant, low thermal expansion coefficient polycarbonate material of the present invention;

[0039] Figure 2 This is a diagram of a flat panel display frame component obtained by injection molding the yellowing-resistant, low thermal expansion coefficient polycarbonate material of the present invention. DETAILED DESCRIPTION

[0040] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0041] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0042] A yellowing-resistant, low thermal expansion coefficient polycarbonate material comprising the following mass components

[0043]

[0044]

[0045] As a preferred solution, the polycarbonate is bisphenol A polycarbonate with a melt index of 15 g / 10 min, and the melt index test conditions are 300° C. / 1.2 kg.

[0046] As a preferred embodiment, the polycarbonate is a mixture of bisphenol A polycarbonate with a melt index of 10 g / 10 min and bisphenol A polycarbonate with a melt index of 20 g / 10 min in a mass ratio of 1:1. This effectively prevents the polycarbonate material from cooling and setting too quickly during injection molding, thereby effectively improving production quality.

[0047] As a preferred solution, the modified titanium dioxide has a rutile titanium dioxide core, and the core is provided with a zinc oxide coating layer, a silicon dioxide coating layer and a triethoxyoctylsilane coating layer in sequence from the inside to the outside.

[0048] Rutile titanium dioxide is one of the most stable crystalline forms of titanium dioxide and has a lower thermal expansion coefficient than anatase titanium dioxide. The zinc oxide coating can further enhance the UV resistance and antibacterial properties of polycarbonate, while also reducing its thermal expansion coefficient. The silica coating effectively prevents aggregation between titanium dioxide particles, further improving the stability of polycarbonate while also effectively enhancing its UV resistance. The triethoxycaprylylsilane coating effectively improves the compatibility of titanium dioxide and significantly enhances the weathering, chemical, and water resistance of polycarbonate. It also reduces friction between polycarbonate molecular chains and increases their fluidity, making them easier to form during processing, reducing energy consumption, and improving production efficiency. This helps produce components with more accurate dimensions and better surface quality.

[0049] As a preferred embodiment, the preparation method of the modified titanium dioxide comprises the following steps:

[0050] S1. Dispersing nano-rutile titanium dioxide in deionized water to obtain titanium dioxide colloids, aging them with zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9 for 5 hours, filtering and washing, and performing azeotropic distillation with n-butanol. After vacuum drying and low-temperature heat treatment, zinc oxide-coated titanium dioxide is obtained;

[0051] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; adding ethyl orthosilicate dropwise to the suspension under constant temperature and stirring for 3 hours, during which the pH value is maintained between 10-11 using a sodium hydroxide solution; after centrifugation, removing the supernatant, washing with deionized water and anhydrous ethanol, filtering, and vacuum drying to obtain composite particles;

[0052] S3. Ultrasonic dispersion of the composite particles prepared in S2 in anhydrous ethanol, addition of triethoxyoctylsilane, and adjustment of the pH to 5.5 with glacial acetic acid. Stirring and reacting at room temperature. Centrifugation and filtration, washing with ethanol, and drying to obtain modified titanium dioxide.

[0053] As a preferred solution, the mass of the zinc sulfate is 3% to 10% of the mass of the rutile titanium dioxide.

[0054] As a preferred solution, the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide. In this way, the thickness of the zinc oxide coating can reach 2-3nm, which can effectively enhance the UV resistance of polycarbonate and reduce the thermal expansion coefficient of polycarbonate by more than 10%.

[0055] As a preferred solution, the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1. 2+ Complete precipitation to form a dense zinc oxide coating.

[0056] As a preferred embodiment, the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21. This ensures that the thickness of the silicon dioxide coating reaches 1 nm. This, in conjunction with the zinc oxide coating, further enhances the polycarbonate's UV resistance, reduces the polycarbonate's thermal expansion coefficient by more than 20%, and imparts excellent mechanical properties and light-shielding properties.

[0057] As a preferred embodiment, the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0058] As a preferred solution, the mass of the triethoxyoctylsilane is 1%-3% of the mass of the composite particles.

[0059] As a preferred solution, the mass of the triethoxyoctylsilane is 1%-1.5% of the mass of the composite particles, which can effectively improve the hydrophobicity of the modified titanium dioxide and improve the compatibility between the modified titanium dioxide and polycarbonate.

[0060] As a preferred embodiment, the toughening agent is a mixture of toughening agents S-2001 and EXL-2620. S-2001, manufactured by Mitsubishi Rayon Co., Ltd. of Japan, effectively improves the stress cracking resistance and flame retardancy of polycarbonate. EXL-2620, manufactured by Rohm and Haas Company of the United States, effectively improves the notch sensitivity and thick-wall brittleness of polycarbonate, while also increasing its toughness and reducing the likelihood of surface flow marks.

[0061] As a preferred solution, the mass ratio of the toughening agent S-2001 to the toughening agent EXL-2620 is 1:3. In fact, the inventors found that the more toughening agent S-2001, the better. If too much toughening agent S-2001 is added, it will reduce the hardness of the polycarbonate, making it too soft and prone to deformation, affecting the overall structural stability and appearance quality of the product; the same is true for the toughening agent EXL-2620. The more the better. If too much toughening agent EXL-2620 is added, the hardness, rigidity and elastic modulus of the polycarbonate will be reduced, which can easily lead to flow marks, spots or other visual defects on the surface of the product. After repeated experiments, the inventors found that when the mass ratio of the toughening agent S-2001 to the toughening agent EXL-2620 is 1:3, it can effectively reduce the internal stress of the polycarbonate, effectively improve the toughness of the polycarbonate, improve the mechanical properties of the polycarbonate, and at the same time reduce the probability of surface flow marks, which helps to obtain parts with better surface quality and improve processing quality.

[0062] As a preferred solution, the lubricant is pentaerythritol stearate, which can improve the thermal stability of polycarbonate on the one hand and make the parts more easily demoulded during processing on the other hand.

[0063] As a preferred embodiment, the antioxidant is tris(2,4-di-tert-butylphenyl)phosphite or β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0064] As a preferred solution, the anti-dripping agent is polytetrafluoroethylene, acrylic acid-coated modified polytetrafluoroethylene or acrylonitrile-styrene-coated modified polytetrafluoroethylene.

[0065] As a preferred embodiment, the flame retardant is potassium perfluorobutanesulfonate.

[0066] The addition of precipitated barium sulfate effectively improves the density, hardness, and wear resistance of polycarbonate. Ethylene-methyl acrylate copolymer improves the compatibility between precipitated barium sulfate and modified titanium dioxide with polycarbonate, while also working synergistically with toughening agents to increase the elastic modulus of polycarbonate. Lubricants effectively reduce melt viscosity and improve processing fluidity, while preventing filler (precipitated barium sulfate and modified titanium dioxide) agglomeration and promoting dispersion. Silicone powder works synergistically with flame retardants to improve the flame retardant efficiency of polycarbonate, while also working synergistically with lubricants to improve the melt fluidity of polycarbonate and enhance its surface smoothness, wear resistance, and scratch resistance.

[0067] A method for preparing the yellowing-resistant, low thermal expansion coefficient polycarbonate material as described above comprises the following steps: adding polycarbonate, modified titanium dioxide, precipitated barium sulfate, a toughening agent, ethylene-methyl acrylate copolymer, a lubricant, an antioxidant, an anti-dripping agent, and silicone powder into a twin-screw extruder, and performing extrusion and granulation to obtain the yellowing-resistant, low thermal expansion coefficient polycarbonate material.

[0068] The specific steps are as follows:

[0069] 1. Weigh polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder in proportion, pour them into the mixing barrel, stir the materials for 10 minutes in advance, then open the discharge port and put the mixed materials into the feed barrel of the twin-screw extruder;

[0070] 2. Turn on the power of the twin-screw extruder and set the temperature of each section of the twin-screw extruder. The temperature of the first zone is set to 250℃, the temperature of the second zone is set to 260℃, the temperature of the third zone is set to 270℃, the temperature of the fourth zone is set to 270℃, the temperature of the fifth zone is set to 270℃, the temperature of the sixth zone is set to 275℃, the temperature of the seventh zone is set to 275℃, the temperature of the eighth zone is set to 280℃, the temperature of the ninth zone is set to 290℃, and the temperature of the die head is set to 300℃.

[0071] 3. After the temperature of each section of the twin-screw extruder reaches the set value, the speed of the twin-screw extruder is set between 350-400r / min, and the speed of the feeder is set between 20-30r / min. After extrusion, passing through a water trough, pelletizing and screening, the yellowing-resistant and low thermal expansion coefficient polycarbonate material is obtained. Figure 1 shown.

[0072] An application of the yellowing-resistant, low thermal expansion coefficient polycarbonate material as described above in the preparation of display back frame components and display frame components. Figure 2 The figure shows a flat panel display frame component obtained by injection molding the above-mentioned yellowing-resistant and low thermal expansion coefficient polycarbonate material.

[0073] The polycarbonate material of the present invention has excellent yellowing resistance, good mechanical properties, low thermal expansion coefficient, good melt fluidity, and is easy to process. Using the polycarbonate material of the present invention for processing, it is easier to obtain components with better surface quality, which can effectively improve the yield of high-quality products. The polycarbonate material of the present invention has strong insulation and good light-shielding properties, and meets the application requirements of display back frame components and display frame components.

[0074] Example 1

[0075] A yellowing-resistant, low thermal expansion coefficient polycarbonate material, the composition of which is as follows:

[0076]

[0077]

[0078] The polycarbonate is prepared by compounding bisphenol A polycarbonate 2200R of Saudi Basic Industries Corporation and bisphenol A polycarbonate IR1810 of Saudi Basic Industries Corporation in a mass ratio of 1:1; the toughening agent is prepared by compounding toughening agent S-2001 and toughening agent EXL-2620 in a mass ratio of 1:3.

[0079] The above modified titanium dioxide is prepared by the following method:

[0080] S1. Dispersing nano-rutile titanium dioxide in deionized water to obtain titanium dioxide colloids, aging the mixture with zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9 for 5 hours, filtering and washing, and azeotropically distilling the mixture with n-butanol. After vacuum drying and low-temperature heat treatment, zinc oxide-coated titanium dioxide is obtained; wherein the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide, and the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1;

[0081] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; adding tetraethyl orthosilicate dropwise to the suspension under constant temperature stirring for 3 hours, during which the pH value is maintained between 10-11 using sodium hydroxide solution; after centrifugation, removing the supernatant, washing with deionized water and anhydrous ethanol, filtering and vacuum drying to obtain composite particles; wherein the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21; and the concentration of the sodium hydroxide solution is 0.1 mol / L;

[0082] S3. Ultrasonic dispersion of the composite particles prepared in S2 in anhydrous ethanol, addition of triethoxyoctylsilane thereto, and adjustment of the pH to 5.5 with glacial acetic acid. The mixture is stirred for reaction at room temperature. After centrifugal filtration, the mixture is rinsed with ethanol and dried to obtain modified titanium dioxide, wherein the mass of the triethoxyoctylsilane is 1% of the mass of the composite particles.

[0083] The method for preparing the above-mentioned yellowing-resistant low thermal expansion coefficient polycarbonate material comprises the following steps:

[0084] 1. Weigh polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder in proportion, pour them into the mixing barrel, stir the materials for 10 minutes in advance, then open the discharge port and put the mixed materials into the feed barrel of the twin-screw extruder;

[0085] 2, turn on the power of the double screw extruder, set the temperature of each section of the double screw extruder, wherein the first zone temperature is set to 250 DEG C, the second zone temperature is set to 260 DEG C, the third zone temperature is set to 270 DEG C, the fourth zone temperature is set to 270 DEG C, the fifth zone temperature is set to 270 DEG C, the sixth zone temperature is set to 275 DEG C, the seventh zone temperature is set to 275 DEG C, the eighth zone temperature is set to 280 DEG C, the ninth zone temperature is set to 290 DEG C, and the die temperature is set to 300 DEG C;

[0086] 3, after the temperature of each section of the double screw extruder reaches the set value, the speed of the double screw extruder is between 350-400r / min, the speed of the feeder is between 20-30r / min, then after extruding, passing through the water tank, cutting and screening, the low thermal expansion coefficient polycarbonate material with yellowing resistance is obtained.

[0087] Example 2

[0088] A low thermal expansion coefficient polycarbonate material with yellowing resistance, the composition is as follows:

[0089]

[0090]

[0091] The polycarbonate is compounded by bisphenol A polycarbonate 2200R of Saudi Basic Industries Corporation and bisphenol A polycarbonate IR1810 of Saudi Basic Industries Corporation in a mass ratio of 1:1; the toughening agent is compounded by toughening agent S-2001 and toughening agent EXL-2620 in a mass ratio of 1:3.

[0092] The modified titanium dioxide powder is made by the following method:

[0093] S1, disperse the nanometer rutile titanium dioxide powder in deionized water to obtain titanium dioxide colloidal particles, use zinc sulfate and sodium carbonate in a pH of 7-9 environment, age for 5 hours, filter and wash, use n-butanol for azeotropic distillation, vacuum drying, low temperature heat treatment, and obtain zinc oxide coated titanium dioxide; wherein the mass of zinc sulfate is 5% of the mass of the red rutile titanium dioxide, and the molar ratio of sodium carbonate to zinc sulfate is 1.1:1;

[0094] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; adding tetraethyl orthosilicate dropwise to the suspension under constant temperature stirring for 3 hours, during which the pH value is maintained between 10-11 using sodium hydroxide solution; after centrifugation, removing the supernatant, washing with deionized water and anhydrous ethanol, filtering and vacuum drying to obtain composite particles; wherein the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21; and the concentration of the sodium hydroxide solution is 0.1 mol / L;

[0095] S3. Ultrasonic dispersion of the composite particles prepared in S2 in anhydrous ethanol, addition of triethoxyoctylsilane thereto, and adjustment of the pH to 5.5 with glacial acetic acid. The mixture is stirred for reaction at room temperature. The mixture is centrifugally filtered, rinsed with ethanol, and dried to obtain modified titanium dioxide, wherein the mass of the triethoxyoctylsilane is 3% of the mass of the composite particles.

[0096] The method for preparing the above-mentioned yellowing-resistant low thermal expansion coefficient polycarbonate material comprises the following steps:

[0097] 1. Weigh polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder in proportion, pour them into the mixing barrel, stir the materials for 10 minutes in advance, then open the discharge port and put the mixed materials into the feed barrel of the twin-screw extruder;

[0098] 2. Turn on the power of the twin-screw extruder and set the temperature of each section of the twin-screw extruder. The temperature of the first zone is set to 250℃, the temperature of the second zone is set to 260℃, the temperature of the third zone is set to 270℃, the temperature of the fourth zone is set to 270℃, the temperature of the fifth zone is set to 270℃, the temperature of the sixth zone is set to 275℃, the temperature of the seventh zone is set to 275℃, the temperature of the eighth zone is set to 280℃, the temperature of the ninth zone is set to 290℃, and the temperature of the die head is set to 300℃.

[0099] 3. After the temperature of each section of the twin-screw extruder reaches the set value, the speed of the twin-screw extruder is adjusted to between 350-400r / min, and the speed of the feeder is adjusted to between 20-30r / min. After extrusion, passing through a water trough, pelletizing, and screening, the yellowing-resistant and low thermal expansion coefficient polycarbonate material is obtained.

[0100] Example 3

[0101] A yellowing-resistant, low thermal expansion coefficient polycarbonate material, the composition of which is as follows:

[0102]

[0103]

[0104] The polycarbonate is prepared by compounding bisphenol A polycarbonate 2200R of Saudi Basic Industries Corporation and bisphenol A polycarbonate IR1810 of Saudi Basic Industries Corporation in a mass ratio of 1:1; the toughening agent is prepared by compounding toughening agent S-2001 and toughening agent EXL-2620 in a mass ratio of 1:3.

[0105] The above modified titanium dioxide is prepared by the following method:

[0106] S1. Dispersing nano-rutile titanium dioxide in deionized water to obtain titanium dioxide colloids, aging the mixture with zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9 for 5 hours, filtering and washing, and azeotropically distilling the mixture with n-butanol. After vacuum drying and low-temperature heat treatment, zinc oxide-coated titanium dioxide is obtained; wherein the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide, and the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1;

[0107] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; adding tetraethyl orthosilicate dropwise to the suspension under constant temperature stirring for 3 hours, during which the pH value is maintained between 10-11 using sodium hydroxide solution; after centrifugation, removing the supernatant, washing with deionized water and anhydrous ethanol, filtering and vacuum drying to obtain composite particles; wherein the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21; and the concentration of the sodium hydroxide solution is 0.1 mol / L;

[0108] S3. Ultrasonic dispersion of the composite particles prepared in S2 in anhydrous ethanol, addition of triethoxyoctylsilane thereto, and adjustment of the pH to 5.5 with glacial acetic acid. The mixture is stirred for reaction at room temperature. The mixture is centrifuged, rinsed with ethanol, and dried to obtain modified titanium dioxide, wherein the mass of the triethoxyoctylsilane is 1.5% of the mass of the composite particles.

[0109] The method for preparing the above-mentioned yellowing-resistant low thermal expansion coefficient polycarbonate material comprises the following steps:

[0110] 1. Weigh polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder in proportion, pour them into the mixing barrel, stir the materials for 10 minutes in advance, then open the discharge port and put the mixed materials into the feed barrel of the twin-screw extruder;

[0111] 2. Turn on the power of the twin-screw extruder and set the temperature of each section of the twin-screw extruder. The temperature of the first zone is set to 250℃, the temperature of the second zone is set to 260℃, the temperature of the third zone is set to 270℃, the temperature of the fourth zone is set to 270℃, the temperature of the fifth zone is set to 270℃, the temperature of the sixth zone is set to 275℃, the temperature of the seventh zone is set to 275℃, the temperature of the eighth zone is set to 280℃, the temperature of the ninth zone is set to 290℃, and the temperature of the die head is set to 300℃.

[0112] 3. After the temperature of each section of the twin-screw extruder reaches the set value, the speed of the twin-screw extruder is adjusted to between 350-400r / min, and the speed of the feeder is adjusted to between 20-30r / min. After extrusion, passing through a water trough, pelletizing, and screening, the yellowing-resistant and low thermal expansion coefficient polycarbonate material is obtained.

[0113] Comparative Example 1

[0114] Preparation of polycarbonate materials

[0115] The difference between this embodiment and Example 3 is that "nano-rutile titanium dioxide" is used instead of "modified titanium dioxide".

[0116] Comparative Example 2

[0117] Preparation of polycarbonate materials

[0118] The difference between it and Example 3 is:

[0119] The modified titanium dioxide is prepared by the following method:

[0120] Nano-rutile titanium dioxide is dispersed in deionized water to obtain titanium dioxide colloids, which are then aged for 5 hours using zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9, filtered and washed, and subjected to azeotropic distillation using n-butanol. The modified titanium dioxide is obtained after vacuum drying and low-temperature heat treatment; wherein the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide, and the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1.

[0121] Comparative Example 3

[0122] Preparation of polycarbonate materials

[0123] The difference between it and Example 3 is:

[0124] The modified titanium dioxide is prepared by the following method:

[0125] S1. Add nano-rutile titanium dioxide to an aqueous solution of n-butanol without adding a dispersant to prepare a titanium dioxide slurry with a concentration of 400 g / L; wherein the volume ratio of n-butanol to water is 3:2;

[0126] S2, adding sodium hydroxide solution to the titanium dioxide slurry to a pH value of 8 to 11, adjusting the slurry temperature to 70° C., and stirring for 20 minutes to obtain a mixed slurry;

[0127] S3. Add silicon dioxide powder to the mixed slurry and stir thoroughly for 30 minutes to allow the silicon dioxide to completely precipitate on the surface of the titanium dioxide. The amount of silicon dioxide added is 3% of the mass of the titanium dioxide.

[0128] Comparative Example 4

[0129] Preparation of polycarbonate materials

[0130] The difference between it and Example 3 is:

[0131] The modified titanium dioxide is prepared by the following method:

[0132] S1. Dispersing nano-rutile titanium dioxide in deionized water to obtain titanium dioxide colloids, aging the mixture with zinc sulfate and sodium carbonate in an environment with a pH of 7 to 9 for 5 hours, filtering and washing, and azeotropically distilling the mixture with n-butanol. After vacuum drying and low-temperature heat treatment, zinc oxide-coated titanium dioxide is obtained; wherein the mass of the zinc sulfate is 5% of the mass of the rutile titanium dioxide, and the molar ratio of the sodium carbonate to the zinc sulfate is 1.1:1;

[0133] S2. Dispersing the zinc oxide-coated titanium dioxide prepared in S1 in a sodium hydroxide solution to form a suspension with a pH value of 10-11; under constant temperature stirring conditions, adding tetraethyl orthosilicate dropwise to the suspension for reaction for 3 hours, during which the pH value is maintained between 10-11 using sodium hydroxide solution. After centrifugation, the supernatant is removed, and the mixture is washed with deionized water and anhydrous ethanol. After filtration and vacuum drying, modified titanium dioxide is obtained; wherein the mass ratio of the tetraethyl orthosilicate to the zinc oxide-coated titanium dioxide is 10:21; and the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0134] Performance testing:

[0135] The yellowing-resistant, low thermal expansion coefficient polycarbonate materials of Examples 1 to 3 and the polycarbonate materials of Comparative Examples 1 to 3 were made into test specimens and then subjected to performance tests. The test results are shown in the following table:

[0136] Table 1 Performance test results of the yellowing-resistant low thermal expansion coefficient polycarbonate materials of Examples 1 to 3 and the polycarbonate materials of Comparative Examples 1 to 3

[0137]

[0138]

[0139] Among them, the above performance test standards and test conditions are shown in Table 2.

[0140] Table 2

[0141]

[0142] As can be seen from Table 1, the thermal expansion coefficients of the yellowing-resistant, low thermal expansion coefficient polycarbonate materials prepared in Examples 1-3 are significantly lower than those of the polycarbonate materials prepared in Comparative Examples 1 and 3, while the thermal expansion coefficients of the polycarbonate materials prepared in Comparative Examples 2 and 4 are comparable to those of Examples 1-3. This is because the modified titanium dioxide in Examples 1-3, 2 and 4 all have a zinc oxide coating layer, while the mechanical properties of Comparative Examples 1-4 are poorer than those of Examples 1-3 and 1, because the polycarbonate materials prepared in Comparative Examples 1-4 all have agglomeration points. This indicates that the triethoxyoctylsilane coating layer can effectively improve the compatibility of titanium dioxide and polycarbonate.

[0143] Yellowing resistance test

[0144] The yellowing-resistant, low thermal expansion coefficient polycarbonate materials of Examples 1 to 3 and the polycarbonate materials of Comparative Examples 1 to 3 were made into test panels with a thickness of 2 mm. Half of the test panels were covered with a light shielding sheet. The test panels were then placed in a yellowing resistance test chamber and irradiated for 96, 120, 144, and 168 hours. The panels were then taken out and the yellowing levels corresponding to the covered and uncovered portions of the test panels were visually evaluated using a gray scale card under a standard light source color matching lamp. The light source was a UVA-340 lamp. During the irradiation process, the temperature was 60±3°C, the humidity was 95%, and the light intensity was 0.5 W / m 2 , the results are shown in Table 2;

[0145] Table 2:

[0146]

[0147] As can be seen from Table 2, the yellowing resistance of the materials prepared in Examples 1-3 and Comparative Example 4 is better than that of the materials prepared in Comparative Examples 1-3. This is because the modified titanium dioxide in Examples 1-3 and Comparative Example 4 all have a zinc oxide coating layer and a silicon dioxide coating layer. The synergistic effect of the zinc oxide coating layer, the silicon dioxide coating layer and the titanium dioxide effectively enhances the UV resistance of the polycarbonate.

[0148] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A yellowing-resistant, low thermal expansion coefficient polycarbonate material, characterized in that: Includes the following quality components 2. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The polycarbonate is bisphenol A polycarbonate with a melt index of 14 to 15 g / 10 min, and the melt index test conditions are 300° C. / 1.2 kg.

3. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The modified titanium dioxide has rutile titanium dioxide as the core, and the core is provided with a zinc oxide coating layer, a silicon dioxide coating layer and a triethoxyoctylsilane coating layer in sequence from the inside to the outside.

4. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 3, characterized in that: The toughening agent is a mixture of toughening agent S-2001 and toughening agent EXL-2620.

5. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The mass ratio of the toughening agent S-2001 to the toughening agent EXL-2620 is 1:

3.

6. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The lubricant is pentaerythritol stearate.

7. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The antioxidant is tris(2,4-di-tert-butylphenyl)phosphite or β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

8. The yellowing-resistant, low thermal expansion coefficient polycarbonate material according to claim 1, characterized in that: The anti-dripping agent is polytetrafluoroethylene, acrylic acid coated modified polytetrafluoroethylene or acrylonitrile-styrene coated modified polytetrafluoroethylene.

9. A method for preparing the yellowing-resistant, low thermal expansion coefficient polycarbonate material according to any one of claims 1 to 8, characterized in that: The following steps are involved: Polycarbonate, modified titanium dioxide, precipitated barium sulfate, toughening agent, ethylene-methyl acrylate copolymer, lubricant, antioxidant, anti-dripping agent and silicone powder are added into a twin-screw extruder, extruded and granulated to obtain yellowing-resistant and low thermal expansion coefficient polycarbonate material.

10. Use of the yellowing-resistant, low thermal expansion coefficient polycarbonate material according to any one of claims 1 to 9 in preparing display frames and back frames.

Images