Preparation method of high-whiteness resin

Abstract

The invention relates to the technical field of resin, in particular to a preparation method of high-whiteness resin, which comprises the following steps: respectively preparing a mesoporous SiO2 (at) Eu < 3 + > whitening agent and a TiO2 photonic crystal whitening agent; the preparation method comprises the following steps: mixing two whitening agents according to a weight ratio of 1: 1-1: 4, carrying out surface modification, and carrying out melt blending with a resin matrix; an intelligent control system is adopted to regulate and control technological parameters in real time, and it is ensured that the whiteness is larger than or equal to 96 and the thermal decomposition temperature is larger than or equal to 380 DEG C. According to the preparation method, a mesoporous SiO2 (at) Eu < 3 + > whitening agent and a TiO2 photonic crystal whitening agent have a synergistic effect, and a silane coupling agent is adopted for surface modification, so that the whitening agents are more evenly and stably dispersed in a resin matrix, and the ultrahigh whiteness larger than or equal to 96 can be achieved; meanwhile, the yellowing risk is reduced, and the visual appearance quality of a resin product is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of resins, and more particularly to a method for preparing high-whiteness resin. Background Art

[0002] In the preparation process of polymer materials such as plastics, fibers or films, it is usually necessary to whiten or brighten the materials to improve the appearance quality and visual appeal. Existing whitening technologies often use inorganic pigments (such as ordinary TiO 2 , calcium carbonate, etc.) or fluorescent brighteners (such as biphenyl type, benzoxazole type fluorescent brighteners) to improve the whiteness and brightness of the product surface. However, traditional brighteners generally have the following shortcomings during use:

[0003] TiO alone 2 Although inorganic pigments such as PET and PE can increase the opacity and whiteness of materials to a certain extent, it is difficult to achieve ultra-high whiteness (CIE Whiteness ≥ 96) which has increasingly higher requirements for visual effects.

[0004] Traditional fluorescent brighteners are prone to decomposition or failure during thermal processing, making it difficult to maintain the whitening effect for a long time.

[0005] Many whitening systems are prone to decomposition or yellowing during high-temperature melt blending or subsequent processing, affecting the appearance stability and service life of the product. For resin products that need to be used for a long time or at high temperatures, if the heat resistance of the whitening agent is poor, it is difficult to ensure that the overall thermal decomposition temperature of the material is ≥380°C, which poses potential safety and quality risks.

[0006] Therefore, how to select whitening materials with both high whiteness and high thermal stability in the resin preparation process, and achieve uniform dispersion, stable bonding and controllable addition of whitening agents in the matrix through reliable surface modification and processing technology, thereby overcoming the problems of insufficient whiteness, low thermal decomposition temperature, poor interface compatibility and lack of online regulation of traditional whitening systems, has become a key technical problem that needs to be solved in this field. Especially in application scenarios with higher requirements for material optical properties and thermal stability (such as high-end electronic materials, automotive interior parts, outdoor weather-resistant products, etc.), it is necessary to further improve the whiteness of the products, reduce the risk of yellowing, and ensure their reliability and processability at higher temperatures. Summary of the invention

[0007] To this end, the object of the present invention is to provide a method for preparing a high-whiteness resin, which can simultaneously meet the requirements of ultra-high whiteness (CIE Whiteness ≥ 96) and relatively high thermal decomposition temperature (≥ 380°C).

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing a high-whiteness resin, comprising the following steps:

[0010] S1. Prepare mesoporous SiO 2 @Eu 3+ whitening agent and TiO 2 photonic crystal whitening agent,

[0011] S2. Mix the two whitening agents in a weight ratio of 1:1 - 1:4, and after surface modification, melt-blend them with the resin matrix;

[0012] S3. Use an intelligent control system to real-time regulate the process parameters to ensure that the whiteness ≥ 96 and the thermal decomposition temperature ≥ 380 °C.

[0013] The present invention is further configured as: The preparation process of the mesoporous SiO 2 @Eu 3+ whitening agent is as follows:

[0014] Dissolve cetyltrimethylammonium bromide in ethanol and mix it in a volume ratio of 4:1, and stir at 40 °C for 30 minutes;

[0015] Dropwise add tetraethyl orthosilicate and react at 40 °C for 6 hours. After centrifugal washing, calcine at 560 - 650 °C for 6 hours to obtain mesoporous SiO 2 ;

[0016] Immerse the obtained mesoporous SiO 2 in a europium nitrate solution with a concentration of 0.1 - 0.5 mol / L and a pH value controlled at 5.5 - 7.5, and ultrasonically treat for 1 - 3 hours to make the Eu 3+ doping amount account for 1 - 5% of the mass of the mesoporous SiO 2 ;

[0017] After vacuum drying at 60 °C, anneal in the way of keeping warm at 200 °C for 1 hour and then raising the temperature to 260 - 350 °C for 2 hours, so as to obtain Eu 3+ uniformly doped and fluorescent whitening effect of mesoporous SiO 2 @Eu 3+ whitening agent.

[0018] The present invention is further configured as: In the step S1, the preparation process of the TiO 2 photonic crystal whitening agent includes:

[0019] Drop tetrabutyl titanate into the ethanol mixture and hydrolyze at 80 °C for 12 hours. After centrifugation, obtain TiO 2 nanospheres with an average particle size of 180 - 220 nm and a particle size dispersion coefficient not exceeding 0.1;

[0020] Disperse the TiO 2 nano - spheres in a 5wt% dispersion liquid and vertically deposit for 48 hours at 45 °C to form a photonic crystal thin film with a thickness of 5 - 10 μm;

[0021] Using atomic layer deposition (ALD), perform 50 cycles of SiCl 4 / H 2 O at 150 °C to grow a 5 - nm - thick SiO 2 coating layer, thereby obtaining a TiO 2 photonic crystal brightener.

[0022] The present invention is further configured as follows: In step S2, when surface - modifying the mixed brightener, the addition amount of the silane coupling agent is 3 - 8% of the weight of the mixed brightener, and the following process is adopted:

[0023] Add the mixed brightener and the silane coupling agent to ethanol according to a weight ratio of 3 - 8%, and perform pre - dispersion at 40 °C for 1 - 2 hours with an ultrasonic power of 200 - 300 W and a frequency of 40 kHz;

[0024] After continuously stirring at 60 °C for 3 hours, vacuum - dry at 80 °C for 6 hours to obtain a modified mass;

[0025] Finally, melt - blend with the resin matrix at 180 - 220 °C and a screw speed of 150 - 250 rpm.

[0026] The present invention is further configured as follows: The surface modification includes:

[0027] Add the mixed brightener and the silane coupling agent to ethanol according to a weight ratio of 3 - 8%, perform ultrasonic treatment at 40 °C for 1 - 2 hours, continuously stir at 60 °C for 3 hours, and vacuum - dry at 80 °C for 6 hours to obtain a mass,

[0028] Adopt a twin - screw extruder for step - by - step temperature - controlled melt - blending, and the process parameters are as follows:

[0029] Feeding section: Add the resin matrix into the twin - screw extruder, control the temperature at 170 - 180 °C, the residence time at 2 - 3 minutes, and the screw speed at 50 - 100 rpm

[0030] Melting section 1: Add the mass into the twin - screw extruder, control the temperature at 190 - 200 °C, the residence time at 2 - 3 minutes, and the screw speed at 150 - 200 rpm;

[0031] Melting section 2: Control the temperature at 200 - 210 °C, the residence time at 3 - 5 minutes, and the screw speed at 200 - 250 rpm;

[0032] Homogenization section: The temperature is controlled at 200 - 210 °C, the residence time is 1 - 2 minutes, vacuum devolatilization is set, and the screw speed is 150 - 180 rpm;

[0033] Die head section: The temperature is controlled at 180 - 190 °C, the residence time is 1 - 3 minutes, and the screw speed is 80 - 120 rpm;

[0034] Among them, during the above-mentioned melt blending process, the screw torque and extrusion pressure are monitored in real time, and appropriate adjustments are made through the intelligent control system to avoid overheating and degradation of the material and ensure uniform dispersion of the whitening agent.

[0035] The present invention is further configured as: The intelligent control system includes:

[0036] A temperature sensor and a PID controller to maintain the temperature fluctuation ≤ ±1 °C;

[0037] An on-line colorimeter detects the whiteness and yellowness index of the extruded strip at a sampling frequency of 1 Hz, and dynamically adjusts the mixing ratio of the mixed whitening agent or the process parameters of the extruder through a feedback algorithm;

[0038] A machine learning model for training and prediction based on historical batch data combined with information such as screw torque, extrusion pressure, and vacuum degree, and real-time optimization of the mixing ratio of the whitening agent and processing parameters.

[0039] The present invention is further configured as: The machine learning model is a neural network, and the input parameters include at least resin type, whitening agent ratio, processing temperature, screw torque, vacuum degree, and extrusion pressure, outputting predicted whiteness and yellowness index, and being able to continuously update the training weights according to the collected data.

[0040] The present invention is further configured as: Before mixing the mesoporous SiO 2 @Eu 3+ whitening agent and TiO 2 photonic crystal whitening agent, the following steps are further included:

[0041] The mesoporous SiO 2 @Eu 3+ whitening agent and TiO 2 photonic crystal whitening agent are respectively subjected to pre-dispersion treatment, dispersed in anhydrous ethanol or other low-polarity solvents, and the aggregates are dissolved by ultrasonic oscillation to ensure monodispersity;

[0042] Adjust the pH value of the dispersion to the neutral range (6 - 7), and stir at 50 - 60 °C for 0.5 - 1 hour to inhibit secondary aggregation;

[0043] The well-dispersed powdery whitening agent is obtained through filtration or centrifugation, and then the two whitening agents are mixed according to the said ratio.

[0044] The present invention is further configured such that: before the resin matrix is added to the twin-screw extruder, it further includes a pre-drying step, that is, the resin matrix is subjected to a drying treatment at 80-120 °C for 2-4 hours to reduce its moisture content to less than 0.1%.

[0045] The present invention is further configured such that: it comprises: resin matrix: 85-95 wt%;

[0046] Mixed whitening agent: 3-10 wt%;

[0047] Optionally, 0.1-2 wt% of antioxidant is added.

[0048] Comparing with the deficiencies of the prior art, the beneficial effects of the present invention are as follows:

[0049] By synergistically combining the mesoporous SiO 2 @Eu 3+ whitening agent and the TiO 2 photonic crystal whitening agent, and performing surface modification with a silane coupling agent, the whitening agent is more uniformly and stably dispersed in the resin matrix, enabling an ultra-high whiteness of CIE Whiteness ≥ 96, reducing the risk of yellowing, and significantly improving the visual appearance quality of resin products. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0051] The following combines the specific process route and formula of the present invention to give a detailed example (or specific implementation manner) to further illustrate the feasibility and superiority of the method for preparing the high-whiteness resin described in the present invention. It should be understood that the following examples are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention; without departing from the essential spirit of the present invention, those skilled in the art can make various deformations, modifications or substitutions, which should all be regarded as falling within the protection scope of the present invention.

[0052] Refer to Figure 1 to further illustrate the preparation method of a high-whiteness resin of the present invention.

[0053] Raw material preparation: Resin matrix - Polypropylene (PP, melt index 12 g / 10 min, grade of a certain industry) is selected as the exemplary matrix resin. Before putting the PP into the twin-screw extruder, it is first dried at 100 °C for 3 hours to reduce the moisture content to about less than 0.1%, reducing the defects and yellowing risk caused by water volatilization during the melt blending process.

[0054] Note: The present invention is also applicable to other thermoplastic resins (such as PET, PA, PC, etc.), and only needs to appropriately adjust parameters such as temperature and screw speed during subsequent melt blending.

[0055] Raw materials of the whitening agent: Cetyltrimethylammonium bromide (CTAB); Tetraethyl orthosilicate (TEOS), analytical pure; Europium nitrate (Eu(NO 3 ) 3 ), analytical pure; Tetrabutyl titanate (TBOT), analytical pure; Absolute ethanol; Silane coupling agent (such as γ-aminopropyltriethoxysilane, etc.).

[0056] Other additives: Antioxidant (optional), such as hindered phenols or phosphites, and the addition amount can be selected within the range of 0.1-2 wt% according to performance requirements; Light stabilizer (optional), such as hindered amines (HALS) or benzotriazoles.

[0057] Necessary instruments include: Ultrasonic instrument (200-300W, 40kHz), high-speed stirrer, vacuum drying oven, twin-screw extruder with temperature-segmented control (equipped with vacuum devolatilization port and on-line detection device), etc.

[0058] Mesoporous SiO 2 @Eu 3+ Preparation of the whitening agent: Dissolve cetyltrimethylammonium bromide (CTAB) in absolute ethanol, and mix according to a volume ratio of 4:1 (ethanol: aqueous solution), and stir at 40 °C for 30 minutes;

[0059] Slowly add tetraethyl orthosilicate (TEOS), and continue to react at 40 °C for 6 hours to generate SiO 2 precursor;

[0060] After centrifugal washing, calcine the product at 560-650 °C for 6 hours to remove the template agent, and obtain mesoporous SiO with an average pore diameter of 2-10 nm and a specific surface area ≥ 300 m² / g 2 powder.

[0061] Eu 3+ Doping modification: Prepare a europium nitrate solution with a concentration of 0.3 mol / L and a pH value of about 6, with the doping amount of Eu 3+ being 3% of the mass of mesoporous SiO 2 as the target;

[0062] Immerse mesoporous SiO 2 into this europium nitrate solution, and treat it under an ultrasonic instrument (power 250W, 40kHz) for 2 hours to ensure that Eu 3+ uniformly penetrates into the mesoporous structure; then carry out vacuum drying at 60 °C to remove the excess solution;

[0063] Preheat the dried solid at 200 °C for 1 hour, then raise the temperature to 320 °C and anneal for 2 hours to obtain Eu 3+ Uniformly doped and fluorescent whitening effect of mesoporous SiO 2 @Eu 3+ Whitening agent.

[0064] TiO 2 Preparation of photonic crystal whitening agent: Drop tetrabutyl titanate (TBOT) into the ethanol-water mixture, control the temperature at 80 °C, and hydrolyze for 12 hours;

[0065] Centrifugally separate to obtain TiO with an average particle size of about 200 nm and a particle size dispersion coefficient not exceeding 0.1 2 Nanospheres; Vacuum dry the product at 60 °C for 6 hours for later use.

[0066] Construction of photonic crystal thin film:

[0067] Disperse the above TiO 2 Nanospheres in a 5 wt% dispersion (volume ratio of absolute ethanol / water 4:1), avoid secondary aggregation through ultrasonic dispersion and stirring;

[0068] Perform vertical deposition at 45 °C for 48 hours to make TiO 2 Nanospheres self-assemble on the substrate to form a photonic crystal thin film with a thickness of 5 - 10 μm;

[0069] Dry the photonic crystal thin film and then peel it off or crush it into a micron-sized flaky structure for later use.

[0070] ALD coating: Using atomic layer deposition (ALD), perform 50 cycles of SiCl 4 / H 2 O at 150 °C to grow a SiO layer with a thickness of about 5 nm; 2 This coating layer can make TiO 2 Photonic crystal whitening agent maintain more stable optical and chemical properties during high-temperature processing.

[0071] Pre-dispersion and mixing of whitening agent: Disperse the above-prepared mesoporous SiO 2 @Eu 3+ Whitening agent and TiO 2 Photonic crystal whitening agent are ultrasonically oscillated for 0.5 - 1 hour with a low-concentration (such as 2 - 3 wt%) solution of absolute ethanol, and stirred at 50 - 60 °C for 0.5 - 1 hour to reduce aggregation; Adjust the pH value of the dispersion to 6 - 7, and filter or centrifuge again to collect the well-dispersed powder.

[0072] Mixed whitening agent: Mix the mesoporous SiO 2 @Eu 3+Whitening agent and TiO 2 The photonic crystal whitening agent is uniformly mixed; or according to the whiteness requirement of the product, the ratio of the two whitening agents is flexibly adjusted within the range of 1:1 to 1:4.

[0073] Surface modification and preparation of the mixed material mass: Take 100 g of the mixed whitening agent powder and add it to an anhydrous ethanol solution containing 3 - 8 wt% (relative to the total mass of the whitening agent) of a silane coupling agent;

[0074] Under the condition of 40 °C, treat it with an ultrasonic power of 250 W and a frequency of 40 kHz for 1 hour to ensure that the particle surface is fully in contact with the coupling agent; then stir at a constant temperature of 60 °C for 3 hours to allow the coupling agent to hydrolyze and condense on the particle surface; finally, dry it under vacuum at 80 °C for 6 hours to obtain a hydrophobically modified whitening agent mass.

[0075] Preliminary batching of the mixed whitening agent and the resin matrix: Premix appropriately according to 90 wt% of the resin matrix, 7 wt% of the whitening agent, and other additives (such as 1 wt% of antioxidant), etc.; if higher weather resistance is required, 0.5 - 1 wt% of a light stabilizer can be added and mixed uniformly for standby.

[0076] Step - type temperature - controlled melt blending process: The above batching is subjected to segmented temperature - controlled melt blending through a twin - screw extruder. Specific parameter examples are as follows (monitored in combination with an online intelligent control system):

[0077] Feeding section:

[0078] Temperature control: 170 - 180 °C

[0079] Residence time: 2 - 3 minutes

[0080] Screw speed: 50 - 100 rpm

[0081] Operation: Continuously feed the dried PP resin matrix into the feeding port of the extruder.

[0082] Melting section 1:

[0083] Temperature control: 190 - 200 °C

[0084] Residence time: 2 - 3 minutes

[0085] Screw speed: 150 - 200 rpm

[0086] Operation: Add the previously prepared modified whitening agent mass in this section; the high - shear effect is beneficial for further dispersion.

[0087] Melting section 2:

[0088] Temperature control: 200 - 210 °C

[0089] Residence time: 3 - 5 minutes

[0090] Screw speed: 200 - 250 rpm

[0091] Operation: The material is fully melted, kneaded, and plasticized to form a uniform melt.

[0092] Homogenizing section:

[0093] Temperature control: 200 - 210 °C

[0094] Residence time: 1 - 2 minutes

[0095] Vacuum devolatilization: -0.07 - -0.09 MPa

[0096] Screw speed: 150 - 180 rpm

[0097] Operation: Eliminate possible residual low molecular substances, moisture, or solvents to prevent degradation and bubble generation.

[0098] Die head section:

[0099] Temperature control: 180 - 190 °C

[0100] Residence time: 1 - 3 minutes

[0101] Screw speed: 80 - 120 rpm

[0102] Operation: Extrude the extruded melt through the die head to obtain a high - whiteness resin strip or particles of a predetermined shape.

[0103] Intelligent control system for online monitoring and dynamic regulation: Install an online colorimeter on the die head section or the cooling conveyor belt after extrusion, with a sampling frequency of 1 Hz, to detect the whiteness and yellowness index of the resin strip in real - time;

[0104] When there is a deviation in whiteness, adjust the addition amount of the whitening agent (if using side feeding or another feeding port) through a feedback algorithm or slightly change the temperature of the melting section to maintain the target whiteness ≥ 96.

[0105] PID temperature control and machine learning optimization: The temperature sensors in each extrusion section work together with the PID controller to maintain the temperature fluctuation ≤ ±1 °C; Record key process parameters such as screw torque, vacuum degree, and extrusion pressure, input them into a pre - trained neural network model, and perform real - time prediction and adaptive adjustment in combination with historical production batch data to prevent thermal degradation and whiteness decline due to excessive shear or high temperature.

[0106] Example 1:

[0107] Raw materials and pretreatment:

[0108] Pre-drying of the resin matrix: Polypropylene (PP) with a melt index of 12 g / 10 min is selected, and the drying conditions are 80 °C for 2 hours to reduce the moisture content to about 0.1% or less.

[0109] Europium nitrate solution: Prepared with a concentration of 0.1 mol / L and a pH of 5.5;

[0110] Eu 3+ Doping amount: 1% of the mass of mesoporous SiO 2 ;

[0111] Mesoporous SiO 2 Annealing: Preheat and hold at 200 °C for 1 hour, then raise the temperature to 260 °C and hold for 2 hours;

[0112] TiO 2 nanospheres: Target particle size within the range of 180 - 220 nm, with 180 nm as the target;

[0113] Thickness of the photonic crystal film: 5 μm;

[0114] ALD coating: SiO 2 with a thickness of 5 nm;

[0115] Ratio of the mixed brightening agent: Mesoporous SiO 2 @Eu 3+ :TiO 2 photonic crystal = 1:1;

[0116] Addition amount of silane coupling agent: 3% of the total mass of the brightening agent.

[0117] Key points for the preparation and modification of the brightening agent:

[0118] Mesoporous SiO 2 @Eu 3+ Prepared under conditions of lower doping concentration and relatively lower temperature annealing;

[0119] TiO 2 The hydrolysis time, vertical deposition time and ALD cycles of the nanospheres all adopt the lower limit values of the range;

[0120] Surface modification: Ultrasonic treatment at 40 °C for 1 hour, stirring at 60 °C for 3 hours, and vacuum drying at 80 °C for 6 hours.

[0121] Batching and melt blending

[0122] PP: 90 wt%, mixed brightening agent: 7 wt%, antioxidant: 1 wt%, other trace additives: 2 wt% (if necessary), pre-mixed and then fed into a twin-screw extruder;

[0123] Segmented temperature control (mainly taking the lower range of each section's temperature and rotation speed):

[0124] Feeding section: 170°C, 2 minutes, screw speed 50 rpm

[0125] Melting section 1: 190°C, 2 minutes, screw speed 150 rpm

[0126] Melting section 2: 200°C, 3 minutes, screw speed 200 rpm

[0127] Homogenizing section: 200°C, 1 minute, vacuum degree -0.07 MPa, screw speed 150 rpm

[0128] Die head section: 180°C, 1 minute, screw speed 80 rpm

[0129] On-line detection: Set on-line colorimeter (sampling frequency 1 Hz), PID temperature control error ≤ ±1°C.

[0130] Example 2:

[0131] Raw materials and pretreatment

[0132] Pre-drying of lipid matrix: 100°C, 3 hours;

[0133] Europium nitrate solution: 0.3 mol / L, pH = 6.5;

[0134] Eu 3+ Doping amount: 3%;

[0135] Mesoporous SiO 2 Annealing: Preheat and keep warm at 200°C for 1 hour, then raise the temperature to 320°C and keep warm for 2 hours;

[0136] TiO 2 Nanospheres: Target particle size is about 200 nm;

[0137] Thickness of photonic crystal film: About 7 μm;

[0138] ALD coating: 5 nm;

[0139] Ratio of mixed optical brightener: 1:2;

[0140] Addition amount of silane coupling agent: 5%.

[0141] Key points for preparation and modification of optical brightener:

[0142] Eu 3+ Median of solution concentration and doping amount to ensure high fluorescence whitening efficiency;

[0143] TiO 2 Hydrolysis, deposition time and number of ALD times are carried out according to conventional standards;

[0144] Modification process: Ultrasonic treatment at 40°C for 1 hour, stirring at 60°C for 3 hours, and vacuum drying at 80°C for 6 hours.

[0145] Ingredient and melt blending

[0146] PP: 90 wt%, mixed brightening agent: 7 wt%, antioxidant: 1 wt%;

[0147] Segmented temperature control (select the middle value):

[0148] Feeding section: 175°C, 2.5 minutes, screw speed 75 rpm

[0149] Melting section 1: 195°C, 2.5 minutes, screw speed 175 rpm

[0150] Melting section 2: 205°C, 4 minutes, screw speed 225 rpm

[0151] Homogenization section: 205°C, 1.5 minutes, vacuum degree -0.08 MPa, screw speed 160 rpm

[0152] Die head section: 185°C, 2 minutes, screw speed 100 rpm

[0153] On-line monitoring: Automatically collect extrusion pressure, screw torque and whiteness. After real-time analysis by the neural network model, if it deviates from the target whiteness, the feeding amount or the temperature of the melting section can be slightly adjusted.

[0154] Example 3:

[0155] Raw materials and pretreatment

[0156] Pre-drying of resin matrix: 120°C, 4 hours;

[0157] Europium nitrate solution: 0.5 mol / L, pH = 7.5;

[0158] Eu 3+ Doping amount: 5%;

[0159] Mesoporous SiO 2 Annealing: Preheat and hold at 200°C for 1 hour, then raise the temperature to 350°C and hold for 2 hours;

[0160] TiO 2 Nanospheres: Take the upper limit value of 220 nm;

[0161] Thickness of photonic crystal film: 10 μm;

[0162] ALD coating: 5 nm;

[0163] Ratio of mixed brightening agent: 1:4;

[0164] Addition amount of silane coupling agent: 8%.

[0165] Key Points in the Preparation and Modification of Whitening Agents

[0166] Eu 3+ Both the concentration and the doping amount are taken as larger values to obtain stronger fluorescence characteristics;

[0167] TiO 2 Self-assembly and ALD processes are carried out under high-end conditions to ensure the best photonic crystal structure;

[0168] Modification process: The upper limits of ultrasonic power and time are (250W, 1 hour), and subsequent drying is carried out at 80°C for 6 hours.

[0169] Ingredient Mixing and Melt Blending

[0170] PP: 90wt%, Mixed Whitening Agent: 7wt%, Antioxidant: 1wt%;

[0171] Segmented Temperature Control (taking high-end parameters):

[0172] Feeding section: 180°C, 3 minutes, screw speed 100rpm

[0173] Melting section 1: 200°C, 3 minutes, screw speed 200rpm

[0174] Melting section 2: 210°C, 5 minutes, screw speed 250rpm

[0175] Homogenization section: 210°C, 2 minutes, vacuum degree -0.09MPa, screw speed 180rpm

[0176] Die head section: 190°C, 3 minutes, screw speed 120rpm

[0177] On-line monitoring: The machine learning model integrates more historical data to dynamically predict the extrusion pressure, torque and whiteness (CIE Whiteness), and adjusts the process in a timely manner to ensure the final high whiteness level.

[0178] Test Results and Comparisons

[0179] The following table lists the main test indexes of three batches of high-whiteness resin samples, including whiteness (CIE Whiteness), yellowness index (YI), thermal decomposition temperature (T5% represents the temperature at 5% weight loss in thermogravimetric analysis) and visual appearance score, etc. Each test is carried out with reference to the corresponding industry or national standards (such as ASTM, GB / T, etc.), and the results are as follows:

[0180]

[0181] Whiteness (CIE Whiteness): It has reached 96.2 in Example 1; 97.3 in Example 2; and further increased to 98.1 in Example 3, showing a significant synergistic whitening and enhanced fluorescence emission effect.

[0182] Yellowness Index (YI): All are significantly lower than the conventional whitening system (usually between 2.0 and 3.5), and it gradually decreases with the improvement of the Eu 3+ doping amount and the TiO 2 photonic crystal structure, indicating that the present invention has a significant improvement effect on optical and thermal stability.

[0183] Thermal decomposition temperature (T5%): All three batches of samples are above 380 °C; it reaches about 388 °C in Example 3, which is better than general whitening modified PP (usually only around 360 - 370 °C), indicating that the present invention has excellent heat resistance.

[0184] Appearance quality: All three batches of samples show uniform white color, and with the strengthening of the whitening system and the improvement of ALD coating, Example 3 has the best optical brightness and uniformity in visual perception.

[0185] From the above three examples and the test data, it can be seen that the method for preparing the high - whiteness resin described in the present invention can indeed maintain excellent optical and thermal stability performance within a relatively wide process window, thus providing a reliable technical approach for the industrial production of high - end whitening resin materials.

[0186] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art's usual changes and substitutions within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high whiteness resin, characterized in that: The steps include: S1. Preparation of mesoporous SiO2@Eu 3+ Brightener and TiO2 photonic crystal brightener; S2, mixing the two brighteners in a weight ratio of 1:1-1:4, and melt-blending them with the resin matrix after surface modification; S3. Use intelligent control system to adjust process parameters in real time to ensure whiteness ≥96 and thermal decomposition temperature ≥380℃.

2. The method for preparing a high whiteness resin according to claim 1, characterized in that: In step S1, mesoporous SiO2@Eu 3+ The preparation process of the brightener is as follows: Dissolve hexadecyltrimethylammonium bromide in ethanol and mix at a volume ratio of 4:1, and stir at 40°C for 30 minutes; Add ethyl silicate dropwise, react at 40°C for 6 hours, centrifuge and wash, and then calcine at 560-650°C for 6 hours to obtain mesoporous SiO2 with an average pore size of 2-10 nm and a specific surface area of ​​≥300 m² / g; The obtained mesoporous SiO2 is immersed in a europium nitrate solution with a concentration of 0.1-0.5 mol / L and a pH value of 5.5-7.5, and ultrasonically treated for 1-3 hours to make Eu 3+ The doping amount accounts for 1-5% of the mass of mesoporous SiO2; After vacuum drying at 60°C, annealing was performed by keeping the temperature at 200°C for 1 hour and then heating to 260-350°C for 2 hours to obtain Eu 3+ Uniformly doped mesoporous SiO2@Eu with fluorescent whitening effect 3+ Brightener.

3. A method for preparing a high whiteness resin according to claim 2, characterized in that: In step S1, the preparation process of the TiO2 photonic crystal brightener comprises: Tetrabutyl titanate was dripped into an ethanol mixture, hydrolyzed at 80°C for 12 hours, and centrifuged to obtain TiO2 nanospheres with an average particle size of 180-220nm and a particle size dispersion coefficient not exceeding 0.1; Dispersing the TiO2 nanospheres in a 5 wt % dispersion solution and vertically depositing at 45° C. for 48 hours to form a photonic crystal film with a thickness of 5 to 10 μm; Atomic layer deposition (ALD) was used to grow a 5 nm thick SiO2 coating layer at 150 °C for 50 SiCl4 / H2O cycles to obtain the TiO2 photonic crystal brightener.

4. The method for preparing a high whiteness resin according to claim 3, characterized in that: In step S2, when the mixed brightener is subjected to surface modification, the amount of the silane coupling agent added is 3 to 8% of the weight of the mixed brightener, and the following process is used: The mixed brightener and the silane coupling agent are added to ethanol at a weight ratio of 3 to 8%, and pre-dispersed at 40°C with an ultrasonic power of 200 to 300 W and a frequency of 40 kHz for 1 to 2 hours; After constant temperature stirring at 60°C for 3 hours, vacuum drying was performed at 80°C for 6 hours to obtain the modified dough; Finally, the mixture is melt-blended with the resin matrix at 180-220° C. and a screw speed of 150-250 rpm.

5. The method for preparing a high whiteness resin according to claim 4, characterized in that: The surface modification includes: The mixed brightener and silane coupling agent are added to ethanol at a weight ratio of 3-8%, and subjected to ultrasonic treatment at 40°C for 1-2 hours, constant temperature stirring at 60°C for 3 hours, and vacuum drying at 80°C for 6 hours to obtain a dough. A twin-screw extruder is used for step-by-step temperature-controlled melt blending, and the process parameters are as follows: Feeding section: Add the resin matrix into the twin-screw extruder, control the temperature to 170-180℃, the residence time to 2-3 minutes, and the screw speed to 50-100rpm Melting stage 1: Add the material mass into the twin-screw extruder, control the temperature at 190-200°C, the residence time at 2-3 minutes, and the screw speed at 150-200rpm; Melting stage 2: temperature controlled at 200-210°C, residence time 3-5 minutes, screw speed 200-250rpm; Homogenization stage: temperature control is 200-210℃, residence time is 1-2 minutes, vacuum devolatilization is set, screw speed is 150-180rpm; Die section: temperature control is 180-190℃, residence time is 1-3 minutes, screw speed is 80-120rpm; In the above-mentioned melt blending process, the screw torque and extrusion pressure are monitored in real time, and appropriate adjustments are made through the intelligent control system to avoid overheating and degradation of the material and ensure uniform dispersion of the whitening agent.

6. The method for preparing a high whiteness resin according to claim 1, characterized in that: The intelligent control system comprises: Temperature sensor and PID controller to maintain temperature fluctuation ≤±1℃; The online colorimeter detects the whiteness and yellowing index of the extruded material strips at a sampling frequency of 1 Hz, and dynamically adjusts the proportion of mixed brighteners or extruder process parameters through feedback algorithms; The machine learning model is used for training and prediction based on historical batch data and combined with information such as screw torque, extrusion pressure, vacuum degree, etc., to optimize the whitening agent mixing ratio and processing parameters in real time.

7. The method for preparing a high whiteness resin according to claim 6, characterized in that: The machine learning model is a neural network, and its input parameters include at least resin type, whitening agent ratio, processing temperature, screw torque, vacuum degree and extrusion pressure. It outputs predicted whiteness and yellowing index, and can continuously update training weights based on collected data.

8. The method for preparing a high whiteness resin according to claim 5, characterized in that: Mesoporous SiO2@Eu 3+ Before the whitening agent and the TiO2 photonic crystal whitening agent are mixed, the following steps are also included: Mesoporous SiO2@Eu 3+ The brightener and TiO2 photonic crystal brightener are pre-dispersed and dispersed in anhydrous ethanol or other low-polarity solvents, and the agglomerates are disintegrated by ultrasonic oscillation to ensure monodispersity; Adjust the pH value of the dispersion to the neutral range (6-7) and stir at 50-60°C for 0.5-1 hour to inhibit secondary agglomeration; The well-dispersed powdered whitening agent is obtained by filtration or centrifugation, and then the two whitening agents are mixed according to the ratio.

9. The method for preparing a high whiteness resin according to claim 5, characterized in that: Before the resin matrix is ​​added into the twin-screw extruder, a pre-drying step is also included, that is, the resin matrix is ​​dried at 80-120° C. for 2-4 hours to reduce its moisture content to below 0.1%.

10. A high whiteness resin, characterized in that: Prepared by the method of any one of claims 1 to 5, comprising: resin matrix: 85-95wt%; Mixed brightener: 3-10wt%; Optionally, 0.1 to 2 wt % of an antioxidant is added.

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