Dispersant optimization method for polaroid limit reliability

Abstract

The invention discloses a method for optimizing a dispersing agent for improving the limit reliability of a polaroid, relates to the technical field of dispersing agent preparation methods, and aims to solve the problems that the use requirement of the polaroid for an intelligent view cabin is that the polaroid can be continuously tested or the working state can be kept for 2000 hours in a high-temperature environment of 140 DEG C, and the existing dispersing agent cannot meet the use requirement. Comprising the following steps: step 1, adding a naphthalene compound and sulfuric acid into a reaction kettle, and continuously stirring under vacuum pressure of the reaction kettle to promote sulfonation reaction to generate a sulfonated product and release low-boiling-point organic matters; step 2, cooling the sulfonated product to 120 DEG C, adding water until the acid value is 20%, cooling, sequentially adding sodium sulfite and ammonium sulfate into the reaction kettle, and stirring at 85 DEG C and normal pressure to generate a macromolecular condensate; 3, adjusting the pH value to 6.5-7.0 by using a sodium hydroxide solution, neutralizing excessive sulfuric acid, and filtering to remove generated sodium sulfate precipitate; and 4, atomizing the liquid product through a spray dryer to obtain the powdery dispersant.

Description

Technical Field

[0001] The present invention relates to the technical field of dispersant preparation methods, in particular to a dispersant optimization method for the ultimate reliability of polarizers. Background Art

[0002] Polarizers are optically functional thin film materials whose core function is to selectively transmit light waves vibrating in a specific direction. They are widely used in liquid crystal displays, organic light-emitting diode displays, 3D glasses, sunglasses, and optical instruments. The core film layer of a polarizer typically achieves its polarization function by dyeing or adsorbing a dichroic dye. Dispersants significantly reduce the surface tension between pigment or dye particles, preventing particle aggregation and ensuring uniform dispersion of the dye within the solution or resin matrix. This is crucial to the polarization performance of the polarizer, as uneven dispersion can lead to localized variations in polarization efficiency and affect display quality. Dispersants form a stable dispersion system, reducing the sedimentation or aggregation of dye particles, thereby ensuring the stability of the polarizer's optical performance during long-term use or storage. For example, in high-temperature and high-humidity environments, dispersants prevent the dye from precipitating or migrating from the PVA film, preventing a decrease in polarization performance or the appearance of color spots. During the polarizer coating or stretching process, dispersants help control the viscosity of the dye solution, ensuring a more uniform film thickness. This is particularly important in the production of large-scale polarizers, as uneven thickness can lead to fluctuations in polarization efficiency, which in turn affects the brightness and contrast of the display panel. Dispersants improve the compatibility between dyes and substrates, enhancing the film's adhesion and flexibility. This is crucial for the durability of polarizers, particularly by reducing the risk of cracking or delamination during subsequent processing or use. The use of dispersants can simplify the polarizer manufacturing process, for example by reducing dye grinding time or lowering the need for high-purity dyes. Dispersants also increase dye utilization, reduce waste, and ultimately lower production costs.

[0003] Chinese Patent Publication No. CN108948787B discloses a dye dispersant and its preparation method. The dye dispersant preparation method comprises the following steps: subjecting a naphthalene compound to a sulfonation reaction with sulfuric acid; collecting low-boiling-point organic matter produced in the sulfonation reaction; and adding the low-boiling-point organic matter to the reaction system of the sulfonation reaction, followed by continued reaction to obtain a sulfonated product. The dye dispersant preparation method of the present invention can reduce the amount of sulfuric acid used, thereby significantly reducing the generation of waste calcium sulfate, achieving environmental protection. Furthermore, the preparation method of the present invention can avoid the problem of product quality degradation due to the introduction of other unidentified substances. Furthermore, the dye dispersant preparation method of the present invention has higher safety, environmental friendliness, and lower cost, making it suitable for large-scale industrial production. The dye dispersant prepared by the method of the present invention has low levels of impurities such as sodium sulfate, calcium ions, and / or magnesium ions, and exhibits excellent properties such as heat stability and stain resistance.

[0004] The above-mentioned existing technical solutions have the following defects: Under the existing dispersion system, continuous testing or maintaining the working state for up to 1000 hours can only be achieved in a high-temperature environment of 140°C. The use requirement of polarizers for smart vision cabins is to continuously perform testing or maintain the working state for up to 2000 hours in a high-temperature environment of 140°C. The existing dispersant cannot meet the use requirements, so we proposed a dispersant optimization method for the extreme reliability of polarizers to solve the above-mentioned problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a dispersant optimization method for the extreme reliability of polarizers, so as to solve the problem raised in the above background technology that the use requirement of polarizers for smart vision cabins is to continuously perform testing or maintain this working state for up to 2000 hours in a high temperature environment of 140°C, and the existing dispersants cannot meet the use requirements.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for optimizing a dispersant for the ultimate reliability of a polarizer, comprising the following steps:

[0007] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, heating the reactor to 130 to 140° C., and continuously stirring for 2 to 3 hours at a reaction pressure of -0.03 to -0.05 MPa to promote the sulfonation reaction and taking samples to test the acid value, thereby generating a sulfonated product and releasing low-boiling-point organic matter;

[0008] Step 2: Cool the sulfonated product to 120°C, add water to make the acid value 20%, and then cool to 80 to 90°C. Then, add sodium sulfite and ammonium sulfate to the reaction kettle in sequence, and stir at 85°C under normal pressure for 1.5 to 2 hours to form a high molecular condensation product.

[0009] Step 3: Adjust the pH to 6.5 to 7.0 with sodium hydroxide solution to neutralize excess sulfuric acid, remove the generated sodium sulfate precipitate by filtration, and control the sodium salt content to be less than or equal to 8%;

[0010] Step 4: Atomize the liquid product through a spray dryer with an inlet temperature of 170 to 183°C and an outlet temperature of 80°C to obtain a powdered dispersion.

[0011] Preferably, in step 1 and step 2, the amount of the naphthalene compound is 42 to 45 parts; the amount of sulfuric acid is 35 to 38 parts; the amount of sodium sulfite is 9 to 10 parts; the amount of ammonium sulfate is 1.3 to 1.6 parts; and the amount of water is 5 to 6 parts.

[0012] Preferably, the naphthalene compound in step 1 is selected from one or more of industrial methylnaphthalene, sodium methylene bisnaphthalene sulfonate and naphthalenesulfonic acid formaldehyde condensate.

[0013] Preferably, the gaseous low-boiling-point organic matter produced by the reaction in step 1 is recovered through a condenser and circulated into the reactor to improve the utilization rate of raw materials and reduce the amount of waste residue.

[0014] Preferably, in step 4, a jet mill is used to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion.

[0015] Compared with existing technologies, the present invention offers the following advantages: The dispersant prepared using naphthalene compounds exhibits strong hydrophobicity and can interact hydrophobically with the surfaces of non-polar particles such as organic dyes and coal dust, forming an anchoring layer and enhancing the dispersant's adsorption capacity on the particle surfaces. Sulfonic acid groups are introduced into the naphthalene compounds through a sulfonation reaction, imparting hydrophilicity to the molecules and creating an amphiphilic structure. This structure enables the dispersant molecules to adsorb simultaneously on the particle surfaces and in the solvent, reducing interparticle interactions and preventing agglomeration. The rigid structure of the naphthalene compounds provides steric hindrance, further hindering particle proximity and improving dispersion stability. In the sulfonation reaction, naphthalene reacts with concentrated sulfuric acid at 160-165°C to produce β-naphthalenesulfonic acid and a small amount of α-naphthalenesulfonic acid. The introduction of sulfonic acid groups imparts hydrophilicity to the molecules. The sulfonated product is hydrolyzed to remove unreacted sulfuric acid and then neutralized with alkali to produce naphthalenesulfonate salts. Naphthalenesulfonate salts condense with formaldehyde under acidic conditions to form linear or branched naphthalenesulfonic acid-formaldehyde condensates, such as the dispersants NNO and MF. The degree of condensation affects molecular weight, which in turn affects dispersibility. The introduction of other monomers, such as styrene sulfonic acid, or additives, such as isooctane and 1-methylimidazole tetrafluoroborate, can optimize the dispersant's heat resistance and water release resistance. The hydrophobicity of naphthalene compounds and the hydrophilicity of the sulfonic acid groups synergistically enable the dispersant to rapidly adsorb onto particle surfaces, significantly reducing system viscosity. For example, in dye grinding, it can improve grinding efficiency by over 30%. It is suitable for use in a variety of fields, including coal-water slurries, dyes, and nanomaterials. Compared to natural dispersants such as lignin sulfonates, naphthalene dispersants have a mature synthesis process, manageable costs, and adjustable molecular weight, facilitating targeted performance optimization. The dispersant in this invention is prepared using sulfuric acid, a core reagent in the sulfonation reaction of naphthalene compounds. During the preparation process, the introduction of sulfonic acid groups causes a sulfonation reaction between sulfuric acid and naphthalene compounds, such as naphthalene or methylnaphthalene, replacing the sulfonic acid groups on the naphthalene ring to form naphthalenesulfonic acid derivatives. This process directly affects the dispersant's hydrophilicity. The reaction must be carried out at a high temperature of 130-140°C under vacuum. The high boiling point and high acidity of sulfuric acid provide stable reaction conditions and prevent side reactions. During the condensation reaction, sulfuric acid catalyzes the hydroxymethylation and polycondensation of sulfonate monomers with formaldehyde, forming linear or branched polymeric dispersants. Sulfuric acid optimizes the reaction process in the following ways: During the condensation stage, such as when naphthalenesulfonic acid and formaldehyde condense to form a polymer, the residual acidic medium accelerates the condensation reaction between aldehydes and sulfonic acid groups, promoting molecular chain extension. The strongly acidic environment inhibits the oxidation or decomposition of naphthalene compounds, ensuring reaction selectivity. During the neutralization step, residual sulfuric acid is treated by neutralizing excess sulfuric acid with sodium hydroxide solution to form a sodium sulfate precipitate, preventing the acidic dispersant from interfering with subsequent dye compatibility. The neutralization converts the sulfonic acid groups into sulfonates, enhancing the dispersant's ionization capacity and electrostatic repulsion of dye particles. Industrial-grade sulfuric acid is low-priced, reducing costs by over 30% compared to other sulfonating agents.Low-boiling-point organic matter volatilized during the reaction can be recovered by condensation and, combined with the stability of sulfuric acid, recycled to reduce pollution. During the grinding of reactive dyes, the sulfuric acid sulfonation product can reduce the dye particle size to 0.8 μm and increase tinting strength by 20%. In the present invention, sulfuric acid is used to prepare the dispersant, and sodium sulfite primarily plays a role in reducing, promoting condensation, and regulating stability. The specific mechanism is as follows: sodium sulfite, as a strong reducing agent, releases sulfite ions under high temperature or acidic conditions. These sulfite preferentially reacts with oxygen or oxidizing substances in the reaction system, protecting raw materials such as naphthalene compounds from oxidative decomposition and ensuring reaction selectivity. During the sulfonation reaction, sodium sulfite synergistically acts with sulfuric acid to promote the sulfonic acid substitution reaction of the naphthalene ring, generating hydrophilic sulfonic acid groups, which are key functional groups for dispersant adsorption of dye particles. When preparing polymer condensation polymer dispersants, sodium sulfite and ammonium sulfate act together as condensation aids, providing sulfite ions to adjust the reaction pH, promote the condensation reaction between formaldehyde and sulfonated naphthalene, and form linear or networked polymer chains, enhancing the steric hindrance effect of the dispersant. The amount of sodium sulfite added affects the condensation rate and the molecular weight distribution of the product, which in turn affects the thermal stability of the dispersant and the thickness of the adsorption layer. In the later stages of the reaction, sodium sulfite reacts with residual sulfuric acid to form sodium sulfate. Adjusting the system pH to 6.5-7.0 reduces the impact of acidity on the dispersant's storage stability. The reducing properties of sodium sulfite prevent oxidation of metal ions in the dye or dispersant molecules, preventing particle agglomeration caused by oxidation and improving the long-term stability of the dispersion. Unconsumed sodium sulfite can be recovered by filtration or combined with other byproducts for treatment, reducing wastewater treatment costs. Compared to other reducing agents, industrial-grade sodium sulfite is inexpensive and can reduce the overall cost of dispersant preparation by over 30%. In this invention, sulfuric acid is used to prepare the dispersant, while ammonium sulfate serves primarily as a neutralizing agent, ionic strength regulator, precipitant, and nitrogen source. As a dispersant, it improves powder dispersibility. Ammonium sulfate is an anionic surfactant. When preparing powders such as YAG, it adsorbs to the positively charged surface of the powder, inhibiting powder agglomeration through electrostatic repulsion, thereby improving dispersion and uniformity. Sulfate ions require high-temperature calcination to eliminate them, and their adsorption properties can further inhibit abnormal particle growth. Ammonium sulfate can be used to optimize reaction conditions by adjusting the pH of the system. For example, in the preparation of YAG powder, when the pH is controlled between 7.5 and 8, the precursor can synthesize a single YAG phase at 900°C, which is significantly lower than the calcination temperature of the solid-phase reaction method. Excessively high pH values ​​can lead to uneven distribution of metal ions in the precipitate, affecting the product synthesis effect. Ammonium sulfate concentration plays a key role in the stability of the aqueous dispersion. When the ammonium sulfate concentration is less than 20%, the salting-out effect is weak, and the polymer cannot be stably dispersed. When the concentration is greater than 35%, the salting-out effect is too strong, causing the aqueous dispersion to stratify. Studies have shown that stable w / w dispersions can be prepared at ammonium sulfate concentrations of 23wt% to 26wt%, and the particle size distribution narrows with increasing concentration.Ammonium sulfate precipitates polymers from the dispersion medium through salting-out, and changes in its concentration directly affect the intrinsic viscosity and apparent viscosity of the polymer. Increasing ammonium sulfate concentration decreases the polymer's hydrophilicity, shortening the precipitation time and critical chain length, leading to lower intrinsic viscosity and bulk viscosity. However, at excessively high concentrations, salting-out shrinks the stabilizer's molecular chains, reducing stabilization effectiveness and causing particle aggregation. The dye dispersant prepared in this invention exhibits excellent compatibility with various dichroic dyes, including azo dichroic dyes, anthraquinone dichroic dyes, triphenoxadiazine and its derivatives, and monomethine and polymethine dichroic dyes. In extreme reliability testing at 140°C for 2160 hours, it demonstrated optical changes, such as absolute changes in polarization, transmittance, and color coordinates, of less than 5%, exceeding the requirements for polarizers used in smart viewing cabins. This addresses the requirement for polarizers used in smart viewing cabins to continuously test or maintain operating conditions for up to 2000 hours at 140°C, a requirement that existing dispersants cannot meet. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0017] Example 1: A dispersant for polarizer extreme reliability, comprising the following steps:

[0018] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, the naphthalene compound having 42 parts and the sulfuric acid having 35 parts, selecting industrial methylnaphthalene and sodium methylenebisnaphthalenesulfonate as the naphthalene compound, heating the reactor to 130° C., stirring continuously for 2 hours at a reaction pressure of −0.03 MPa, promoting a sulfonation reaction, sampling and testing the acid value, generating a sulfonated product and releasing low-boiling-point organic matter, recovering the gaseous low-boiling-point organic matter produced by the reaction through a condenser, and circulating the recovered gaseous low-boiling-point organic matter in the reactor to improve raw material utilization and reduce waste residue.

[0019] Step 2: Cool the sulfonated product to 120°C, add water to adjust the acid value to 20%, and then cool to 82°C. Add sodium sulfite and ammonium sulfate in sequence to the reaction kettle, and stir at 85°C under normal pressure for 1.5 hours to form a high molecular condensation product, wherein the parts of sodium sulfite are 9 parts, the parts of ammonium sulfate are 1.4 parts, and the parts of water are 5 parts;

[0020] Step 3: Adjust the pH to 6.5 with sodium hydroxide solution to neutralize excess sulfuric acid, filter out the generated sodium sulfate precipitate, control the sodium salt content to be less than or equal to 8%, and use a jet mill to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion;

[0021] Step 4: The liquid product was atomized by a spray dryer with an inlet temperature of 170°C and an outlet temperature of 80°C to obtain a powdered dispersant.

[0022] Example 2: A polarizer extreme reliability dispersant comprising the following steps:

[0023] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, the naphthalene compound having 43 parts and the sulfuric acid having 35 parts, wherein industrial methylnaphthalene is selected as the naphthalene compound, heating the reactor to 132° C., stirring continuously for 2.5 hours at a reaction pressure of −0.03, promoting a sulfonation reaction, sampling and testing the acid value, generating a sulfonation product and releasing low-boiling-point organic matter, recovering the gaseous low-boiling-point organic matter generated by the reaction through a condenser, and circulating the recovered gaseous low-boiling-point organic matter in the reactor to improve raw material utilization and reduce waste residue.

[0024] Step 2: Cool the sulfonated product to 120° C., add water to adjust the acid value to 20%, and then cool to 85° C., add sodium sulfite and ammonium sulfate in sequence to a reaction kettle, and stir at 85° C. under normal pressure for 1.7 hours to form a high molecular condensation product, wherein the parts of sodium sulfite are 9 parts, the parts of ammonium sulfate are 1.4 parts, and the parts of water are 6 parts;

[0025] Step 3: Adjust the pH to 6.5 with sodium hydroxide solution to neutralize excess sulfuric acid, filter out the generated sodium sulfate precipitate, control the sodium salt content to be less than or equal to 8%, and use a jet mill to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion;

[0026] Step 4: The liquid product was atomized by a spray dryer with an inlet temperature of 175°C and an outlet temperature of 80°C to obtain a powdered dispersant.

[0027] Example 3: A dispersant for polarizer extreme reliability, comprising the following steps:

[0028] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, the naphthalene compound having 45 parts and the sulfuric acid having 36 parts, wherein sodium methylenebisnaphthalenesulfonate and naphthalenesulfonic acid formaldehyde condensate are selected as the naphthalene compound, heating the reactor to 140° C., stirring continuously for 3 hours at a reaction pressure of 0.05 MPa, promoting a sulfonation reaction, sampling and testing the acid value, generating a sulfonated product and releasing low-boiling organic matter, recovering the gaseous low-boiling organic matter produced by the reaction through a condenser, and circulating the recovered gaseous low-boiling organic matter in the reactor to improve raw material utilization and reduce the amount of waste residue;

[0029] Step 2: Cool the sulfonated product to 120°C, add water to adjust the acid value to 20%, and then cool to 88°C. Add sodium sulfite and ammonium sulfate in sequence to the reaction kettle, and stir at 85°C under normal pressure for 2 hours to form a high molecular condensation product, wherein the sodium sulfite is 10 parts, the ammonium sulfate is 1.6 parts, and the water is 6 parts;

[0030] Step 3: Adjust the pH to 7.0 with sodium hydroxide solution to neutralize excess sulfuric acid, filter out the generated sodium sulfate precipitate, control the sodium salt content to be less than or equal to 8%, and use a jet mill to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion;

[0031] Step 4: The liquid product was atomized by a spray dryer with an inlet temperature of 170°C and an outlet temperature of 80°C to obtain a powdered dispersant.

[0032] Example 4: A polarizer extreme reliability dispersant comprising the following steps:

[0033] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, the naphthalene compound to be 45 parts, and the sulfuric acid to be 38 parts, wherein industrial methylnaphthalene is selected as the naphthalene compound, heating the reactor to 136° C., stirring continuously for 2.5 hours at a reaction pressure of −0.04 MPa, promoting a sulfonation reaction, sampling and testing the acid value, generating a sulfonation product and releasing low-boiling-point organic matter, recovering the gaseous low-boiling-point organic matter generated by the reaction through a condenser, and circulating the recovered gaseous low-boiling-point organic matter in the reactor to improve raw material utilization and reduce waste residue.

[0034] Step 2: Cool the sulfonated product to 120°C, add water to adjust the acid value to 20%, and then cool to 90°C. Add sodium sulfite and ammonium sulfate in sequence to the reaction kettle, and stir at 85°C under normal pressure for 2 hours to form a high molecular condensation product. The sodium sulfite is 10 parts, the ammonium sulfate is 1.5 parts, and the water is 5 parts.

[0035] Step 3: Adjust the pH to 6.7 with sodium hydroxide solution to neutralize excess sulfuric acid, filter out the generated sodium sulfate precipitate, control the sodium salt content to be less than or equal to 8%, and use a jet mill to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion;

[0036] Step 4: The liquid product was atomized by a spray dryer with an inlet temperature of 183°C and an outlet temperature of 80°C to obtain a powdered dispersant.

[0037] Example 5: A dispersant for polarizer extreme reliability, comprising the following steps:

[0038] Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, the naphthalene compound being 45 parts in number and the sulfuric acid being 338 parts in number, sodium methylenebisnaphthalenesulfonate being selected as the naphthalene compound, heating the reactor to 140° C., stirring continuously for 3 hours at a reaction pressure of −0.05 MPa, promoting a sulfonation reaction, sampling and testing the acid value, generating a sulfonated product and releasing low-boiling-point organic matter, recovering the gaseous low-boiling-point organic matter produced by the reaction through a condenser, and circulating the recovered gaseous low-boiling-point organic matter in the reactor to improve raw material utilization and reduce waste residue volume;

[0039] Step 2: Cool the sulfonated product to 120°C, add water to adjust the acid value to 20%, and then cool to 90°C. Add sodium sulfite and ammonium sulfate in sequence to a reaction kettle, and stir at 85°C under normal pressure for 1.5 seconds to form a high molecular condensation product, wherein the parts of sodium sulfite are 9 parts, the parts of ammonium sulfate are 1.6 parts, and the parts of water are 6 parts;

[0040] Step 3: Adjust the pH to 7.0 with sodium hydroxide solution to neutralize excess sulfuric acid, filter out the generated sodium sulfate precipitate, control the sodium salt content to be less than or equal to 8%, and use a jet mill to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion;

[0041] Step 4: The liquid product was atomized by a spray dryer with an inlet temperature of 183°C and an outlet temperature of 80°C to obtain a powdered dispersant.

[0042] By testing this dispersant, the optical stability of the polarizer under extreme test conditions is improved. It also has good water solubility in the range of 35°C to 70°C, ≥10g / 100gH2O; it has good neutrality retention ability after water dissolution, and the pH value remains in the range of 6.5 to 7.0 after 144 hours. It has good compatibility with dichroic dyes of different components, such as azo dichroic dyes, anthraquinone dichroic dyes, triphenoxadiazine and derivative dichroic dyes, monomethine and polymethine dichroic dyes.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for optimizing the dispersant for the ultimate reliability of polarizers, characterized in that: The following steps are involved: Step 1: adding a naphthalene compound and sulfuric acid to a reactor, controlling the sulfuric acid concentration to 98%, heating the reactor to 130 to 140° C., and continuously stirring for 2 to 3 hours at a reaction pressure of -0.03 to -0.05 MPa to promote the sulfonation reaction and taking samples to test the acid value, thereby generating a sulfonated product and releasing low-boiling-point organic matter; Step 2: Cool the sulfonated product to 120°C, add water to make the acid value 20%, and then cool to 80 to 90°C. Then, add sodium sulfite and ammonium sulfate to the reaction kettle in sequence, and stir at 85°C under normal pressure for 1.5 to 2 hours to form a high molecular condensation product. Step 3: Adjust the pH to 6.5 to 7.0 with sodium hydroxide solution to neutralize excess sulfuric acid, remove the generated sodium sulfate precipitate by filtration, and control the sodium salt content to be less than or equal to 8%; Step 4: Atomize the liquid product through a spray dryer with an inlet temperature of 170 to 183°C and an outlet temperature of 80°C to obtain a powdered dispersion.

2. The method for optimizing the dispersant for the ultimate reliability of polarizer according to claim 1, wherein: In the steps 1 and 2, the proportion of the naphthalene compound is 42 to 45 parts; the proportion of sulfuric acid is 35 to 38 parts; the proportion of sodium sulfite is 9 to 10 parts; the proportion of ammonium sulfate is 1.3 to 1.6 parts; and the proportion of water is 5 to 6 parts.

3. The method for optimizing the dispersant for the ultimate reliability of polarizer according to claim 1, wherein: In the step 1, the naphthalene compound is selected from one or more of industrial methylnaphthalene, sodium methylene bisnaphthalene sulfonate and naphthalenesulfonic acid formaldehyde condensate.

4. The method for optimizing the dispersant for the ultimate reliability of polarizers according to claim 1, wherein: In step 1, the gaseous low-boiling-point organic matter produced by the reaction is recovered through a condenser and circulated into the reactor to improve the utilization rate of raw materials and reduce the amount of waste residue.

5. The method for optimizing the dispersant for the ultimate reliability of polarizer according to claim 1, wherein: In step 4, a jet mill is used to adjust the powder particle size to less than 50 μm to ensure uniformity during dye dispersion.