Yellowing-resistant polystyrene resin for optical plates and preparation method of yellowing-resistant polystyrene resin

Abstract

The invention relates to the technical field of polystyrene resin and a preparation method thereof, in particular to yellowing-resistant polystyrene resin for an optical plate and a preparation method thereof, the yellowing-resistant polystyrene resin for the optical plate comprises specific amounts of styrene monomer, a molecular weight regulator, a slipping agent, a polymerization solvent, an antioxidant, an antioxidant auxiliary agent, a light stabilizer and an ultraviolet absorbent. According to the preparation method disclosed by the invention, by adding a specific amount of additives such as the antioxidant, the antioxidant adjuvant, the ultraviolet absorbent and the light stabilizer, the prepared polystyrene resin material has the characteristics of high purity, high light transmittance, low chromaticity, low residual monomer content and the like; the thermo-oxidative aging resistance and the ultraviolet aging resistance of the polystyrene resin material can be improved, the aging time of the material is delayed, the long-term yellowing resistance effect is achieved, and the polystyrene resin material is particularly suitable for manufacturing optical-grade plates.

Description

Technical Field

[0001] The invention relates to the technical field of polystyrene resin and preparation method thereof, in particular to yellowing-resistant polystyrene resin for optical plates and preparation method thereof. Background Art

[0002] Polystyrene is suitable for manufacturing optical plates. In the prior art, polystyrene products introduce trace coloring additives to ensure a low yellowness index of the product. Although the addition of coloring additives can reduce the yellowness index of existing products, the optical plates are sensitive to blue light during use, which can lead to a decline in product quality. Therefore, they can only be used for low-end optical plates.

[0003] In the prior art, polystyrene products age and turn yellow during production, processing and long-term use, which greatly reduces the service life of the products. Summary of the invention

[0004] In view of this, the present invention provides a yellowing-resistant polystyrene resin for optical plates and a preparation method of the yellowing-resistant polystyrene resin for optical plates.

[0005] Specifically, the present invention is achieved through the following technical solutions: According to a first aspect of the present invention, a yellowing-resistant polystyrene resin for optical plates is provided, comprising: a styrene monomer, the styrene monomer is 95 to 99.8 parts; a molecular weight regulator, the molecular weight regulator is 0 to 0.5 parts; a lubricant, the lubricant is 0 to 0.1 parts; a polymerization solvent, the polymerization solvent is 0 to 5 parts; an antioxidant, the antioxidant is 0.05 to 0.2 parts; an antioxidant auxiliary, the antioxidant auxiliary is 0.05 to 0.2 parts; a light stabilizer, the light stabilizer is 0.02 to 0.2 parts; and an ultraviolet absorber is 0.02 to 0.2 parts.

[0006] The yellowing-resistant polystyrene resin for optical plates proposed in the present application (hereinafter referred to as polystyrene resin material) includes styrene monomer, molecular weight regulator, lubricant, polymerization solvent, antioxidant, antioxidant auxiliary and light stabilizer, wherein styrene monomer is the main component of polystyrene resin material, molecular weight regulator can adjust the molecular weight distribution of polystyrene during polymerization, molecular weight regulator can be mineral white oil, the weight percentage of molecular weight regulator is 0 to 0.5 parts, when the amount of molecular weight regulator added is greater than 0.5 parts, the transmittance of styrene monomer after polymerization will be reduced. Lubricant is used to improve the fluidity of materials and is beneficial to material mixing, the weight percentage of lubricant is 0 to 0.1 parts, when the amount of lubricant added is greater than 0.1 parts, the transmittance of styrene monomer after polymerization will be reduced. The polymerization solvent can be toluene or ethylbenzene, the weight percentage of polymerization solvent is 0 to 5 parts. Antioxidants are used to improve the oxidation resistance of materials. Polystyrene is prone to thermal oxidation aging during high-temperature processing and under sunlight, causing the material to become brittle and yellow. The oxidation resistance of the material can be improved by adding antioxidants to polystyrene resin materials. The weight percentage of antioxidants is 0.05 to 0.2 parts. If the amount of antioxidant added is less than 0.05 parts, the antioxidant effect of the material will be poor. If the amount of antioxidant added is greater than 0.2 parts, the light transmittance of the styrene monomer after polymerization will be reduced. Antioxidant adjuvants can work synergistically with antioxidants to improve the oxidation resistance of polystyrene resin materials and delay the aging process of the material. The weight percentage of antioxidant adjuvants is 0.05 to 0.2 parts. If the amount of antioxidant adjuvant added is less than 0.05 parts, the antioxidant effect of the material will be poor. If the amount of antioxidant adjuvant added is greater than 0.2 parts, the light transmittance of the styrene monomer after polymerization will be reduced. The weight percentages of light stabilizer and ultraviolet absorber are both 0.02 parts to 0.2 parts. Polystyrene resin materials are prone to ultraviolet aging when used for a long time under light and sunlight conditions, causing the color of the material to turn yellow and the transmittance to decrease. By adding light stabilizer and ultraviolet absorber to the polystyrene resin material, the material's resistance to ultraviolet aging can be improved. If the added amounts of both the light stabilizer and the ultraviolet absorber are less than 0.02 parts, the polystyrene resin material will have poor resistance to ultraviolet aging. If the added amounts of both the light stabilizer and the ultraviolet absorber are greater than 0.2 parts, the transmittance after the polymerization of the styrene monomer will be reduced.

[0007] By setting the composition of the polystyrene resin material to include styrene monomer, molecular weight regulator, lubricant, polymerization solvent, antioxidant, antioxidant auxiliary and light stabilizer, the heat-oxidative aging resistance and ultraviolet aging resistance of the polystyrene resin material can be improved, and the aging time of the material can be delayed. At the same time, the high purity, high transmittance and low chromaticity of the polystyrene resin material can be ensured.

[0008] In some technical schemes, the lubricant is zinc stearate, the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl), the antioxidant auxiliary is tris(2,4-di-tert-butylbenzene) phosphite, the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole.

[0009] In this technical solution, the lubricant, antioxidant auxiliary, light stabilizer and ultraviolet absorber are specifically defined. Among them, the lubricant is zinc stearate, so that the finished product made of polystyrene resin material can obtain extremely high surface finish and smoothness. Further, the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl), and the antioxidant auxiliary is tris(2,4-di-tert-butylbenzene) phosphite, and the two work synergistically to improve the antioxidant properties of polystyrene resin materials. Further, the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, both of which can improve the anti-ultraviolet aging performance of polystyrene resin materials.

[0010] According to a second aspect of the present invention, a method for preparing a polystyrene resin material is provided, which is used to prepare the polystyrene resin material provided by the first aspect of the present invention, and the preparation method comprises: dehydrating and adsorbing styrene monomers to reduce the moisture content in the styrene monomers to obtain a pretreated raw material; subjecting the pretreated raw material to a prepolymerization reaction to obtain a prepolymer product; subjecting the prepolymer product to multiple polymerization reactions to obtain a polymer product, and in at least one of the multiple polymerization reactions, mixing the polymer product with a styrene additive solution, the styrene additive solution comprising styrene, an antioxidant, an antioxidant auxiliary and a light stabilizer; subjecting the polymer product to a devolatilization treatment and a purification treatment to reduce the content of styrene monomer in the polymer product to obtain a devolatilized material; and subjecting the devolatilized material to a process to obtain a polystyrene resin material.

[0011] The preparation method of the polystyrene resin material proposed in the present application is used to prepare the polystyrene resin material proposed in the first aspect of the present invention. The specific preparation method is as follows: First, the polystyrene monomer is dehydrated to reduce the moisture in the polystyrene monomer. The water content of the treated styrene monomer is ≤50μg / g. Optionally, the moisture content of the styrene monomer after dehydration is in the range of 35μg / g to 50μg / g. Then the polystyrene monomer is subjected to adsorption treatment, and the adsorption treatment is used to remove TBC (4-tert-Butylcatechol tert-butylcatechol) and a small amount of residual moisture in the styrene monomer. The adsorbent used in the adsorption treatment can be alumina, and the adsorption treatment can be carried out in a dedicated adsorption equipment. After the dehydration treatment and adsorption treatment of the polystyrene monomer, a pretreated raw material can be obtained, and the components of the pretreated raw material are still polystyrene monomer.

[0012] Understandably, the moisture content and TBC content in the polystyrene resin material have a greater impact on the yellowness index of the polystyrene resin material. By reducing the water content and TBC content in the styrene monomer, a polystyrene resin material with lower chroma can be produced, which has a positive effect on the light transmittance of optical plates made of polystyrene resin materials.

[0013] Then, the pretreated raw material is subjected to a prepolymerization reaction to obtain a prepolymer product. Specifically, the prepolymerization reaction can be carried out by thermal initiation, and the prepolymerization reaction can be carried out in a reactor with a stirring device, and the reactor can be one or multiple reactors connected in series. When the prepolymerization is completed, the conversion rate of styrene monomer to polymer is 60% to 70%, so as to obtain a prepolymer product. Wherein, the water content of the styrene monomer is less than or equal to 30 μg / g, and the tert-butyl catechol content is ≤1 μg / g.

[0014] After obtaining the prepolymer product, the prepolymer product is subjected to multiple polymerization reactions to improve the conversion rate of the polymer to obtain a polymer product. Specifically, in at least one polymerization reaction among the multiple polymerization reactions, the polymer product is mixed with a styrene addition solution, which includes styrene, an antioxidant, an antioxidant auxiliary, an ultraviolet absorber and a light stabilizer to improve the anti-ultraviolet aging performance and anti-oxidation performance of the polystyrene resin material. The polymerization reaction can be carried out under the conditions of both the lubricant and the molecular weight regulator being present, neither of them being present, and one of them being present.

[0015] After obtaining the polymer product, the polymer product is subjected to devolatilization and purification treatment to reduce the content of polystyrene monomer in the polymer product. It is understandable that after the prepolymerization reaction and the polymerization reaction, a small amount of polystyrene monomer will still remain in the polymer product. The content of polystyrene monomer in the polymer product can be reduced by devolatilization and purification treatment. Specifically, the content of polystyrene monomer remaining in the polymer product is ≤200 μg / g, and the devolatilized material is obtained.

[0016] After obtaining the devolatilized material, the devolatilized material is processed to obtain a polystyrene resin material. Specifically, the process can be a finished product granulation process, where the devolatilized material is pumped to a granulation extrusion system, extruded into strands, and then enters a strand cooling water bath, and then pelletized, dried, and sieved to obtain a granular polystyrene resin material. The process can also be other processes to obtain polystyrene resin materials in other forms.

[0017] By using the above preparation method to prepare polystyrene resin materials, the product can be kept stable after the introduction of light stabilizers, antioxidants and other additives, and the material's resistance to thermal oxidation aging can be improved. The polystyrene resin material prepared by this preparation method has the characteristics of high purity, high light transmittance, low chromaticity, low residual monomers, etc., and can delay the aging time to achieve a long-term yellowing resistance effect, and is particularly suitable for making optical-grade plates.

[0018] In some technical schemes, the pretreated raw material is subjected to a prepolymerization reaction, specifically including: placing the pretreated raw material in a reaction vessel, heating the reaction vessel to 145° C. to 157° C., reacting for 3 h to 3.5 h, and stirring the pretreated raw material at a speed of 19 r / min to 21 r / min.

[0019] In this technical solution, the step of subjecting the pretreated raw material to a prepolymerization reaction is specifically defined. After obtaining the pretreated raw material, the pretreated raw material is placed in a reaction vessel, and the process conditions of the prepolymerization reaction can be controlled as follows: the reaction vessel is heated to 145°C to 157°C, that is, the temperature of the prepolymerization reaction is 145°C to 157°C, the reaction time is 3h to 3.5h, and the pretreated raw material in the reaction vessel is stirred at a speed of 19r / min to 21r / min. When the prepolymerization reaction is completed, the conversion rate of styrene monomer to polymer is 60% to 70%, wherein the moisture content of styrene monomer in the prepolymer product is less than or equal to 30μg / g, and the content of tert-butyl catechol is ≤1μg / g.

[0020] In some technical schemes, the prepolymer product is subjected to multiple polymerization reactions, specifically including: placing the prepolymer product in a first reactor, a second reactor and a third reactor in sequence for multiple polymerization reactions, placing a styrene addition solution in the second reactor when the prepolymer product is subjected to polymerization reaction in the second reactor, and the polymerization reaction can be carried out in the presence of both a lubricant and a molecular weight regulator, or in the absence of both, or in the presence of one of them.

[0021] In the technical scheme, the step of subjecting the prepolymer product to multiple polymerization reactions is specifically defined. After obtaining the prepolymer product, the prepolymer product is placed in a reactor for polymerization reaction. The reactor includes a first reactor, a second reactor and a third reactor connected in series, and the prepolymer product is successively subjected to polymerization reaction in the first reactor, the second reactor and the third reactor to improve the conversion rate of polystyrene monomer into polymer. At the same time, the polymerization reaction can be carried out under the conditions of both the lubricant and the molecular weight regulator being present, neither of them being present, and one of them being present. Wherein, when the prepolymer product is subjected to polymerization reaction in the second reactor, the styrene addition solution is placed in the second reactor to finally obtain the polymerization product.

[0022] In some technical schemes, the temperature in the first reactor is 140°C to 160°C, the temperature in the second reactor is 1°C to 3°C higher than the temperature in the first reactor, and the temperature in the third reactor is 1°C to 3°C higher than the temperature in the second reactor.

[0023] In this technical solution, the process conditions of the polymerization reaction are specifically defined, wherein when the prepolymer is polymerized in the first reactor, the second reactor and the third reactor respectively, the temperature in the first reactor is 140°C to 160°C, the temperature in the second reactor is 141°C to 161°C, and the temperature in the third reactor is 142°C to 165°C. Further, the temperature in the second reactor is 1°C to 3°C higher than the temperature in the first reactor, and the temperature in the third reactor is 1°C to 3°C higher than the temperature in the second reactor.

[0024] Furthermore, the melt mass flow rate is controlled to be less than or equal to 4 g / 10 min, and the total polymerization reaction time, that is, the total residence time of the prepolymer product in a single reactor, can be ≤90 min, for example, 80 min to 90 min. At this time, the conversion rate of the polymer is 70% to 80%.

[0025] In some technical schemes, the lubricant is zinc stearate, and the mass ratio of the prepolymer product to the lubricant is 100:(0 to 1.0); the molecular weight regulator is mineral white oil, and the mass ratio of the prepolymer product to the molecular weight regulator is 100:(0 to 5).

[0026] In this technical solution, the lubricant and molecular weight regulator added in the polymerization reaction are defined. The lubricant is zinc stearate, and the mass ratio of the prepolymer product to the lubricant is 100: (0 to 1.0), so as to improve the fluidity of the material while avoiding reducing the transmittance of the styrene monomer after polymerization. The molecular weight regulator is mineral white oil, and the mass ratio of the prepolymer product to the molecular weight regulator is 100: (0 to 5) to avoid reducing the transmittance of the styrene monomer after polymerization.

[0027] In some technical schemes, the polymerization product is subjected to devolatilization and purification treatments, specifically including: devolatilization of the polymerization product at a temperature of 220°C to 250°C and an absolute pressure of 0.1 kPa to 8 kPa; purification of the polymerization product at a temperature of 50°C to 60°C.

[0028] In this technical solution, the devolatilization treatment and purification treatment of the polymerization product are specifically defined. The process conditions of the devolatilization treatment are: the devolatilization treatment is carried out at a temperature of 220°C to 250°C and an absolute pressure of 0.1kPa to 8kPa. The content of polystyrene monomer remaining in the polymerization product after the devolatilization treatment is ≤200μg / g. The purification treatment is carried out in a purification tower, and during the purification treatment, the temperature at the bottom of the purification tower is 50°C to 60°C. The content of polystyrene monomer in the polymerization product after the devolatilization treatment and purification treatment is reduced to ≤200μg / g, and the specific content of polystyrene monomer can be reduced to 120μg / g to 180μg / g to obtain a devolatilized material.

[0029] In some technical schemes, the devolatilization treatment includes a first devolatilization treatment stage, a second devolatilization treatment stage and a third devolatilization treatment stage, wherein the temperature of the first devolatilization treatment stage is 220°C to 230°C and the absolute pressure is 0.1kPa to 0.25kPa, the temperature of the second devolatilization treatment stage is 225°C to 240°C and the absolute pressure is 7kPa to 8kPa, and the temperature of the third devolatilization treatment stage is 230°C to 250°C and the absolute pressure is 7kPa to 8kPa.

[0030] In this technical solution, the devolatilization treatment is further defined. The devolatilization treatment can be carried out in three stages, wherein the treatment temperature of the first devolatilization treatment stage is 220°C to 230°C and the absolute pressure is 0.1kPa to 0.25kPa; the treatment temperature of the second devolatilization treatment stage is 225°C to 240°C and the absolute pressure is 7Pa to 8kPa; the treatment temperature of the third devolatilization treatment stage is 230°C to 250°C and the absolute pressure is 7kPa to 8kPa. This treatment method is easy to reduce the residual polystyrene monomer content in the prepolymer product to a range of ≤200μg / g, especially, the residual polystyrene monomer content in the polymer product is controlled at 120μg / g to 180μg / g to obtain the devolatilized material.

[0031] In some technical solutions, before the styrene monomer is subjected to dehydration treatment and adsorption treatment, the method further includes: dissolving an antioxidant, an antioxidant auxiliary and a light stabilizer in styrene to obtain a styrene addition solution.

[0032] In this technical solution, before the styrene monomer is subjected to dehydration and adsorption treatment, a material configuration step is also included. The material configuration step is specifically: dissolving styrene, antioxidant, antioxidant auxiliary and light stabilizer in styrene to obtain a styrene added solution, and injecting the styrene added solution into a storage tank for standby use.

[0033] The technical solution provided by the present invention brings at least the following beneficial effects: by setting the components of the polystyrene resin material to include styrene monomer, molecular weight regulator, lubricant, polymerization solvent, antioxidant, antioxidant auxiliary and light stabilizer, the heat-oxidative aging resistance and ultraviolet aging resistance of the polystyrene resin material can be improved, the aging time of the material can be delayed, and at the same time, the high purity, high light transmittance and low chroma of the polystyrene resin material can be ensured.

[0034] Additional aspects and advantages of the present invention will become apparent from the following description or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0037] Figure 1One of the schematic flow charts of the method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 2 A second schematic flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 3 A third flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 4 A fourth flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 5 A fifth flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 6 A sixth flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 7 A seventh flow chart of a method for preparing a polystyrene resin material provided in an embodiment of the present invention; Figure 8 A schematic diagram of a route for a method for preparing a polystyrene resin material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The present invention provides a yellowing-resistant polystyrene resin for optical plates, comprising: a styrene monomer, wherein the styrene monomer is 95 to 99.8 parts; a molecular weight regulator, wherein the molecular weight regulator is 0 to 0.5 parts; a lubricant, wherein the lubricant is 0 to 0.1 parts; a polymerization solvent, wherein the polymerization solvent is 0 to 5 parts; an antioxidant, wherein the antioxidant is 0.05 to 0.2 parts; an antioxidant auxiliary, wherein the antioxidant auxiliary is 0.05 to 0.2 parts; a light stabilizer, wherein the light stabilizer is 0.02 to 0.2 parts; and an ultraviolet absorber, wherein the ultraviolet absorber is 0.02 to 0.2 parts.

[0040] The yellowing-resistant polystyrene resin for optical plates proposed in the present application includes styrene monomer, molecular weight regulator, lubricant, polymerization solvent, antioxidant, antioxidant auxiliary and light stabilizer, wherein styrene monomer is the main component of polystyrene resin material, molecular weight regulator can adjust the molecular weight distribution of polystyrene during polymerization, molecular weight regulator can be mineral white oil, the weight percentage of molecular weight regulator is 0 to 0.5 parts, when the amount of molecular weight regulator added is greater than 0.5 parts, the transmittance of styrene monomer after polymerization will be reduced. Lubricant is used to improve the fluidity of materials and is conducive to material mixing, the weight percentage of lubricant is 0 to 0.1 parts, when the amount of lubricant added is greater than 0.1 parts, the transmittance of styrene monomer after polymerization will be reduced. The polymerization solvent can be toluene or ethylbenzene, the weight percentage of polymerization solvent is 0 to 5 parts. Antioxidants are used to improve the oxidation resistance of materials. Polystyrene is prone to thermal oxidation aging during high-temperature processing and under sunlight, causing the material to become brittle and yellow. The oxidation resistance of the material can be improved by adding antioxidants to polystyrene resin materials. The weight percentage of antioxidants is 0.05 to 0.2 parts. If the amount of antioxidant added is less than 0.05 parts, the antioxidant effect of the material will be poor. If the amount of antioxidant added is greater than 0.2 parts, the light transmittance of the styrene monomer after polymerization will be reduced. Antioxidant adjuvants can work synergistically with antioxidants to improve the oxidation resistance of polystyrene resin materials and delay the aging process of the material. The weight percentage of antioxidant adjuvants is 0.05 to 0.2 parts. If the amount of antioxidant adjuvant added is less than 0.05 parts, the antioxidant effect of the material will be poor. If the amount of antioxidant adjuvant added is greater than 0.2 parts, the light transmittance of the styrene monomer after polymerization will be reduced. The weight percentages of light stabilizer and ultraviolet absorber are both 0.02 parts to 0.2 parts. Polystyrene resin materials are prone to ultraviolet aging when used for a long time under light and sunlight conditions, causing the color of the material to turn yellow and the transmittance to decrease. By adding light stabilizer and ultraviolet absorber to the polystyrene resin material, the material's resistance to ultraviolet aging can be improved. If the added amounts of both the light stabilizer and the ultraviolet absorber are less than 0.02 parts, the polystyrene resin material will have poor resistance to ultraviolet aging. If the added amounts of both the light stabilizer and the ultraviolet absorber are greater than 0.2 parts, the transmittance after the polymerization of the styrene monomer will be reduced.

[0041] By setting the composition of the polystyrene resin material to include styrene monomer, molecular weight regulator, lubricant, polymerization solvent, antioxidant, antioxidant auxiliary and light stabilizer, the heat-oxidative aging resistance and ultraviolet aging resistance of the polystyrene resin material can be improved, and the aging time of the material can be delayed. At the same time, the high purity, high transmittance and low chromaticity of the polystyrene resin material can be ensured.

[0042] In some embodiments, the lubricant is zinc stearate, the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl), the antioxidant auxiliary is tris(2,4-di-tert-butylbenzene) phosphite, the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole.

[0043] In this embodiment, the lubricant, antioxidant auxiliary, light stabilizer and ultraviolet absorber are specifically defined. Among them, the lubricant is zinc stearate, so that the finished product made of polystyrene resin material can obtain extremely high surface finish and smoothness. Further, the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl), and the antioxidant auxiliary is tris(2,4-di-tert-butylbenzene) phosphite, and the two work synergistically to improve the antioxidant properties of the polystyrene resin material. Further, the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole, both of which can improve the anti-ultraviolet aging performance of the polystyrene resin material.

[0044] Based on the same inventive concept, as attached Figure 1 As shown, the present invention provides a method for preparing a yellowing-resistant polystyrene resin for optical plates, comprising the following steps: S101: performing dehydration and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; S103: subjecting the pretreated raw material to a prepolymerization reaction to obtain a prepolymerization product; S105: subjecting the prepolymer product to multiple polymerization reactions to obtain a polymerization product, and in at least one polymerization reaction among the multiple polymerization reactions, mixing the polymerization product with a styrene addition solution, wherein the styrene addition solution includes styrene, an antioxidant, an antioxidant auxiliary, an ultraviolet absorber, and a light stabilizer; S107: performing devolatilization and purification treatment on the polymerization product to reduce the content of styrene monomer in the polymerization product to obtain a devolatilized material; S109: Processing the devolatilized material to obtain yellowing-resistant polystyrene resin for optical plates.

[0045] The preparation method of the yellowing-resistant polystyrene resin for optical plates proposed in the present application is specifically as follows; first, the polystyrene monomer is dehydrated to reduce the moisture in the polystyrene monomer, and the water content of the styrene monomer after the treatment is ≤50μg / g. Optionally, the moisture content of the styrene monomer after the dehydration treatment ranges from 35μg / g to 50μg / g. Then, the polystyrene monomer is subjected to an adsorption treatment, and the adsorption treatment is used to remove TBC and a small amount of residual moisture in the styrene monomer. The adsorbent used in the adsorption treatment can be alumina, and the adsorption treatment can be carried out in a dedicated adsorption equipment. After the dehydration treatment and adsorption treatment of the polystyrene monomer, a pretreated raw material can be obtained, and the component of the pretreated raw material is still the polystyrene monomer.

[0046] Understandably, the moisture content and TBC content in the polystyrene resin material have a greater impact on the yellowness index of the polystyrene resin material. By reducing the water content and TBC content in the styrene monomer, a polystyrene resin material with lower chroma can be produced, which has a positive effect on the light transmittance of optical plates made of polystyrene resin materials.

[0047] Then, the pretreated raw material is subjected to a prepolymerization reaction to obtain a prepolymer product. Specifically, the prepolymerization reaction can be carried out by thermal initiation, and the prepolymerization reaction can be carried out in a reactor with a stirring device, and the reactor can be one or multiple reactors connected in series. When the prepolymerization is completed, the conversion rate of styrene monomer to polymer is 60% to 70%, so as to obtain a prepolymer product. Wherein, the water content of the styrene monomer is less than or equal to 30 μg / g, and the tert-butyl catechol content is ≤1 μg / g.

[0048] After obtaining the prepolymer product, the prepolymer product is subjected to multiple polymerization reactions to improve the conversion rate of the polymer to obtain a polymer product. Specifically, in at least one polymerization reaction among the multiple polymerization reactions, the polymer product is mixed with a styrene addition solution, which includes styrene, an antioxidant, an antioxidant auxiliary agent, and a light stabilizer to improve the anti-ultraviolet aging performance and anti-oxidation performance of the polystyrene resin material. The polymerization reaction can be carried out under the conditions of both the lubricant and the molecular weight regulator being present, neither of them being present, and one of them being present.

[0049] After obtaining the polymer product, the polymer product is subjected to devolatilization and purification treatment to reduce the content of polystyrene monomer in the polymer product. It is understandable that after the prepolymerization reaction and the polymerization reaction, a small amount of polystyrene monomer will still remain in the polymer product. The content of polystyrene monomer in the polymer product can be reduced by devolatilization and purification treatment. Specifically, the content of polystyrene monomer remaining in the polymer product is ≤200 μg / g, and the devolatilized material is obtained.

[0050] After obtaining the devolatilized material, the devolatilized material is processed to obtain a polystyrene resin material. Specifically, the process can be a finished product granulation process, where the devolatilized material is pumped to a granulation extrusion system, extruded into strands, and then enters a strand cooling water bath, and then pelletized, dried, and sieved to obtain a granular polystyrene resin material. The process can also be other processes to obtain polystyrene resin materials in other forms.

[0051] By using the above preparation method to prepare polystyrene resin materials, the product can be kept stable after the introduction of light stabilizers, antioxidants and other additives, and the material's resistance to thermal oxidation aging can be improved. The polystyrene resin material prepared by this preparation method has the characteristics of high purity, high light transmittance, low chromaticity, low residual monomers, etc., and can delay the aging time to achieve a long-term yellowing resistance effect, and is particularly suitable for making optical-grade plates.

[0052] like Figure 2 As shown, in some embodiments, the method for preparing the polystyrene resin material comprises the following steps: S201: performing dehydration and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; S203: placing the pretreated raw material in a reaction vessel, heating the reaction vessel to 145° C. to 157° C., reacting for 3 h to 3.5 h, stirring the pretreated raw material at a speed of 19 r / min to 21 r / min to obtain a prepolymer product; S205: subjecting the prepolymer product to multiple polymerization reactions to obtain a polymerization product, and in at least one polymerization reaction among the multiple polymerization reactions, mixing the polymerization product with a styrene addition solution, wherein the styrene addition solution includes styrene, an antioxidant, an antioxidant auxiliary agent, and a light stabilizer; S207: performing devolatilization and purification treatment on the polymerization product to reduce the content of styrene monomer in the polymerization product to obtain a devolatilized material; S209: Processing the devolatilized material to obtain a polystyrene resin material.

[0053] In this embodiment, the step of subjecting the pretreated raw material to a prepolymerization reaction is specifically defined. After obtaining the pretreated raw material, the pretreated raw material is placed in a reaction vessel, and the process conditions of the prepolymerization reaction can be controlled as follows: the reaction vessel is heated to 145°C to 157°C, that is, the temperature of the prepolymerization reaction is 145°C to 157°C, the reaction time is 3h to 3.5h, and the pretreated raw material in the reaction vessel is stirred at a speed of 19r / min to 21r / min. When the prepolymerization reaction is completed, the conversion rate of styrene monomer to polymer is 60% to 70%, wherein the moisture content of styrene monomer in the prepolymer product is less than or equal to 30μg / g, and the content of tert-butyl catechol is ≤1μg / g.

[0054] like Figure 3 As shown, in some embodiments, the method for preparing the polystyrene resin material comprises the following steps: S301: performing dehydration treatment and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; S303: placing the pretreated raw material in a reaction vessel, heating the reaction vessel to 145° C. to 157° C., reacting for 3 h to 3.5 h, stirring the pretreated raw material at a speed of 19 r / min to 21 r / min to obtain a prepolymer product; S305: placing the prepolymer product in the first reactor, the second reactor and the third reactor in sequence to perform multiple polymerization reactions, placing the styrene addition solution in the second reactor while the prepolymer product is undergoing polymerization reaction, the polymerization reaction may be performed under the conditions of the simultaneous presence of the lubricant and the molecular weight regulator, the absence of both, or the presence of one of them, to obtain a polymerization product, and in at least one polymerization reaction among the multiple polymerization reactions, mixing the polymerization product with the styrene addition solution, the styrene addition solution comprising styrene, an antioxidant, an antioxidant auxiliary and a light stabilizer; S307: performing devolatilization and purification treatment on the polymerization product to reduce the content of styrene monomer in the polymerization product to obtain a devolatilized material; S309: Processing the devolatilized material to obtain a polystyrene resin material.

[0055] In this embodiment, the step of subjecting the prepolymer product to multiple polymerization reactions is specifically defined. After obtaining the prepolymer product, the prepolymer product is placed in a reactor to perform a polymerization reaction. The reactor includes a first reactor, a second reactor and a third reactor connected in series, and the prepolymer product is successively subjected to polymerization reactions in the first reactor, the second reactor and the third reactor to increase the conversion rate of polystyrene monomer into polymer. At the same time, the polymerization reaction can be carried out under the conditions of the simultaneous presence of a lubricant and a molecular weight regulator, the absence of both, and the presence of one of them. Wherein, when the prepolymer product is subjected to a polymerization reaction in the second reactor, a styrene addition solution is placed in the second reactor to finally obtain a polymer product.

[0056] In some embodiments, the temperature in the first reactor is 140°C to 160°C, the temperature in the second reactor is 1°C to 3°C higher than the temperature in the first reactor, and the temperature in the third reactor is 1°C to 3°C higher than the temperature in the second reactor.

[0057] In this embodiment, the process conditions of the polymerization reaction are specifically defined, wherein when the prepolymer is polymerized in the first reactor, the second reactor and the third reactor respectively, the temperature in the second reactor is 1°C to 3°C higher than the temperature in the first reactor, and the temperature in the third reactor is 1°C to 3°C higher than the temperature in the second reactor.

[0058] Furthermore, the melt mass flow rate is controlled to be less than or equal to 4 g / 10 min, and the total polymerization reaction time, that is, the total residence time of the prepolymer product in a single reactor, can be ≤90 min, for example, 80 min to 90 min. At this time, the conversion rate of the polymer is 70% to 80%.

[0059] In some embodiments, the lubricant is zinc stearate, and the mass ratio of the prepolymer product to the lubricant is 100:(0 to 1.0); the molecular weight regulator is mineral white oil, and the mass ratio of the prepolymer product to the molecular weight regulator is 100:(0 to 5).

[0060] In this embodiment, the lubricant and molecular weight regulator added in the polymerization reaction are limited. The lubricant is zinc stearate, and the mass ratio of the prepolymer product to the lubricant is 100: (0 to 1.0), so as to improve the fluidity of the material while avoiding reducing the transmittance of the styrene monomer after polymerization. The molecular weight regulator is mineral white oil, and the mass ratio of the prepolymer product to the molecular weight regulator is 100: (0 to 5) to avoid reducing the transmittance of the styrene monomer after polymerization.

[0061] like Figure 4 As shown, in some embodiments, the method for preparing the polystyrene resin material comprises the following steps: S401: performing dehydration treatment and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; S403: placing the pretreated raw material in a reaction vessel, heating the reaction vessel to 145° C. to 157° C., reacting for 3 h to 3.5 h, stirring the pretreated raw material at a speed of 19 r / min to 21 r / min to obtain a prepolymer product; S405: placing the prepolymer product in the first reactor, the second reactor and the third reactor in sequence to perform multiple polymerization reactions, placing the styrene addition solution in the second reactor while the prepolymer product is undergoing polymerization reaction, the polymerization reaction may be performed under the conditions of the simultaneous presence of the lubricant and the molecular weight regulator, the absence of both, or the presence of one of them, to obtain a polymerization product, and in at least one polymerization reaction among the multiple polymerization reactions, mixing the polymerization product with the styrene addition solution, the styrene addition solution comprising styrene, an antioxidant, an antioxidant auxiliary and a light stabilizer; S407: Devolatilizing the polymer product at a temperature of 220° C. to 250° C. and an absolute pressure of 0.1 kPa to 8 kPa; S409: Purifying the polymerization product at a temperature of 50° C. to 60° C. to obtain a devolatilized material; S411: Processing the devolatilized material to obtain a polystyrene resin material.

[0062] In this embodiment, the devolatilization treatment and purification treatment of the polymer product are specifically defined. The process conditions of the devolatilization treatment are: the devolatilization treatment is carried out at a temperature of 220°C to 250°C and an absolute pressure of 0.1kPa to 8kPa. The content of polystyrene monomer remaining in the polymer product after the devolatilization treatment is ≤200μg / g. The purification treatment is carried out in a purification tower, and during the purification treatment, the temperature at the bottom of the purification tower is 50°C to 60°C. The content of polystyrene monomer in the polymer product after the devolatilization treatment and the purification treatment is reduced to ≤200μg / g, and the specific content of polystyrene monomer can be reduced to 120μg / g to 180μg / g to obtain a devolatilized material.

[0063] In some embodiments, the devolatilization treatment includes a first devolatilization treatment stage, a second devolatilization treatment stage and a third devolatilization treatment stage, wherein the temperature of the first devolatilization treatment stage is 220°C to 230°C and the absolute pressure is 0.1 kPa to 0.25 kPa, the temperature of the second devolatilization treatment stage is 225°C to 240°C and the absolute pressure is 7 kPa to 8 kPa, and the temperature of the third devolatilization treatment stage is 230°C to 250°C and the absolute pressure is 7 kPa to 8 kPa.

[0064] In this embodiment, the devolatilization treatment is further defined. The devolatilization treatment can be divided into three stages, wherein the treatment temperature of the first devolatilization treatment stage is 220°C to 230°C and the absolute pressure is 0.1kPa to 0.25kPa; the treatment temperature of the second devolatilization treatment stage is 225°C to 240°C and the absolute pressure is 7Pa to 8kPa; the treatment temperature of the third devolatilization treatment stage is 230°C to 250°C and the absolute pressure is 7kPa to 8kPa. This treatment method is easy to reduce the residual polystyrene monomer content in the prepolymer product to a range of ≤200μg / g, especially, the residual polystyrene monomer content in the polymer product is controlled at 120μg / g to 180μg / g to obtain the devolatilized material.

[0065] like Figure 5 As shown, in some embodiments, the method for preparing the polystyrene resin material comprises the following steps: S501: dissolving an antioxidant, an antioxidant auxiliary and a light stabilizer in styrene to obtain a styrene added solution; S503: performing dehydration treatment and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; S505: placing the pretreated raw material in a reaction vessel, heating the reaction vessel to 145° C. to 157° C., reacting for 3 h to 3.5 h, stirring the pretreated raw material at a speed of 19 r / min to 21 r / min to obtain a prepolymer product; S507: placing the prepolymer product in the first reactor, the second reactor and the third reactor in sequence to perform multiple polymerization reactions, placing the styrene addition solution in the second reactor while the prepolymer product is undergoing polymerization reaction, the polymerization reaction may be performed under the conditions of the simultaneous presence of the lubricant and the molecular weight regulator, the absence of both, or the presence of one of them, to obtain a polymerization product, and in at least one polymerization reaction among the multiple polymerization reactions, mixing the polymerization product with the styrene addition solution, the styrene addition solution comprising styrene, an antioxidant, an antioxidant auxiliary and a light stabilizer; S509: performing devolatilization treatment on the polymerization product at a temperature of 220° C. to 250° C. and an absolute pressure of 0.1 kPa to 8 kPa; S511: Purifying the polymerization product at a temperature of 50° C. to 60° C. to obtain a devolatilized material; S513: Processing the devolatilized material to obtain a polystyrene resin material.

[0066] In this embodiment, before the styrene monomer is subjected to dehydration and adsorption treatment, a material configuration step is also included. The material configuration step is specifically: dissolving styrene, antioxidant, antioxidant auxiliary and light stabilizer in styrene to obtain a styrene added solution, and injecting the styrene added solution into a storage tank for standby use.

[0067] The present invention will be further described below in conjunction with embodiments: like Figure 6 As shown, Example 1: The method for preparing the yellowing-resistant polystyrene resin for optical plates comprises the following steps: S601: 97 parts by weight of styrene monomer and 3 parts by weight of ethylbenzene are sent to a prepolymerization reactor for prepolymerization reaction at a prepolymerization temperature of 142° C. for a prepolymerization time of 3 hours to obtain a prepolymerized product; wherein the water content in the styrene monomer is 20 μg / g, and the content of tert-butylcatechol is 0.6 μg / g; and the conversion rate of the prepolymerized product is 66%; S603: The prepolymer product is sent to a three-stage series polymerization reactor for polymerization reaction, and a styrene addition solution is added to the second reactor. The temperature of the first reactor is 140°C, the temperature of the second reactor is 142°C, and the temperature of the third reactor is 145°C. The melt mass flow rate in the last polymerization kettle reactor is controlled to be 4.0g / 10min, and the total residence time of the polymerization reaction is 200min to obtain a polymerization product; wherein the conversion rate of the polymerization product is 79%, and the styrene addition solution includes styrene, an antioxidant (β-(3,5-di-tert-butyl-4-hydroxyphenyl)) 0.05 parts, an antioxidant auxiliary (tris(2,4-di-tert-butylphenyl) phosphite) 0.1 parts, an ultraviolet absorber (2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole) 0.02 parts, and a light stabilizer (bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate) 0.1 parts; S605: The polymerization product is sent to a three-stage devolatilizer for devolatilization treatment, wherein the temperature of the first stage devolatilizer is 220°C and the absolute pressure is 0.2kPa, the temperature of the second stage devolatilizer is 225°C and the absolute pressure is 5KPa, and the temperature of the third stage devolatilizer is 235°C and the absolute pressure is 7KPa. Then, the polymerization product after the devolatilization treatment is sent to a granulation unit for stranding and pelletizing to obtain yellowing-resistant polystyrene resin for optical plates and a preparation method thereof.

[0068] Comparative Example 1: The difference from the above-mentioned Example 1 is that the raw materials include 0.1 parts by weight of a lubricant (zinc stearate) and 0.2 parts by weight of an antioxidant (tri(2,4-di-tert-butyl)phenyl phosphite), and the remaining steps are the same.

[0069] like Figure 7As shown, Example 2: A method for preparing a yellowing-resistant polystyrene resin for an optical plate comprises the following steps: S701: 97 parts by weight of styrene monomer and 3 parts by weight of ethylbenzene are sent to a prepolymerization reactor for prepolymerization reaction at a prepolymerization temperature of 142° C. for a prepolymerization time of 3 hours to obtain a prepolymerized product; wherein the water content in the styrene monomer is 25 μg / g, and the content of tert-butylcatechol is 0.8 μg / g; and the conversion rate of the prepolymerized product is 68%; S703: The prepolymer product is sent to a three-stage series polymerization reactor for polymerization reaction, and a styrene addition solution is added to the second reactor. The temperature of the first reactor is 140°C, the temperature of the second reactor is 142°C, and the temperature of the third reactor is 145°C. The melt mass flow rate in the last polymerization kettle reactor is controlled to be 2.0g / 10min, and the total residence time of the polymerization reaction is 200min to obtain a polymerization product; wherein the conversion rate of the polymerization product is 82%, and the styrene addition solution includes styrene, an antioxidant (β-(3,5-di-tert-butyl-4-hydroxyphenyl)) 0.2 parts, an antioxidant auxiliary (tris(2,4-di-tert-butylphenyl) phosphite) 0.2 parts, an ultraviolet absorber (2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole) 0.1 parts, and a light stabilizer (bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate) 0.02 parts; S705: The polymerization product is sent to a three-stage devolatilizer for devolatilization treatment, wherein the temperature of the first stage devolatilizer is 220°C and the absolute pressure is 0.2kPa, the temperature of the second stage devolatilizer is 225°C and the absolute pressure is 5KPa, and the temperature of the third stage devolatilizer is 235°C and the absolute pressure is 7KPa. Then, the polymerization product after the devolatilization treatment is sent to a granulation unit for stranding and pelletizing to obtain yellowing-resistant polystyrene resin for optical plates and a preparation method thereof.

[0070] Comparative Example 2: The difference from the above-mentioned Example 2 is that the raw materials further include 0.2 parts by weight of a lubricant (liquid paraffin), and the remaining steps are the same.

[0071] The performance of Examples 1 and 2 of the present invention and Comparative Examples 1 and 2 was investigated, and the performance indicators investigated included Vicat softening temperature (°C), transmittance (%), and yellow index before and after thermal oxidative aging, and yellow index before and after ultraviolet aging. The test results are shown in Table 1. It can be seen from Table 1 that, compared with the comparative example of the present invention, the transmittance of the polystyrene resin material for optical plates of the present invention is above 92%, the yellow index is about -6.0, and the yellow index increases less after thermal oxidative aging and ultraviolet aging. It shows that the preparation method of the present invention makes the obtained yellowing-resistant polystyrene resin for optical plates and its preparation method have higher light transmittance and good appearance performance on the basis of yellowing resistance, and can better meet the sensory needs of consumers for product appearance.

[0072] In summary, in the preparation method of the present invention, by adding specific amounts of additives such as antioxidants, antioxidant auxiliary agents, ultraviolet absorbers and light stabilizers, the prepared yellowing-resistant polystyrene resin for optical plates and the preparation method thereof have the characteristics of high purity, high light transmittance, low chroma, low residual monomers, etc., and can improve the thermal oxygen aging resistance and ultraviolet aging resistance of the yellowing-resistant polystyrene resin for optical plates and the preparation method thereof, delay the aging time of the material, and achieve a long-term yellowing resistance effect, which is particularly suitable for the production of optical-grade plates.

[0073] As attached Figure 2 As shown, the technical route of the preparation method of the yellowing-resistant polystyrene resin for optical plates and the preparation method thereof provided by the present invention is: the styrene monomer removes the polymerization inhibitor (TBC) in the alumina adsorption tower, is mixed with the styrene monomer recovered by the condensation system, and is sent to the reactor, and a 50% to 70% conversion is completed in the CSTR reactor (Continuous Stirred Tank Reactor continuous stirring reactor system) (the conversion rate varies with the product brand). After the CSTR, the styrene addition solution is directly added after metering. The material after adding the styrene addition solution enters the plunger flow reactor, and after completing 70% to 85% conversion, it enters the devolatilization system to remove the residual monomers.

[0074] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0075] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A yellowing-resistant polystyrene resin for optical plates, characterized in that: The raw materials include by weight: Styrene monomer, wherein the styrene monomer is 95 parts to 99.8 parts; A molecular weight regulator, wherein the molecular weight regulator is 0 to 0.5 parts; A lubricant, wherein the lubricant is 0 to 0.1 parts; A polymerization solvent, wherein the polymerization solvent is 0 to 5 parts; Antioxidant, the antioxidant is 0.05 to 0.2 parts; An antioxidant auxiliary agent, wherein the antioxidant auxiliary agent is 0.05 to 0.2 parts; Light stabilizer, the light stabilizer is 0.02 to 0.2 parts; The ultraviolet absorber is 0.02 to 0.2 parts.

2. The yellowing-resistant polystyrene resin for optical plates according to claim 1, characterized in that: The lubricant is zinc stearate; the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl); the antioxidant auxiliary is tris(2,4-di-tert-butylbenzene) phosphite; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; and the ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octyl)phenylbenzotriazole.

3. A method for preparing a yellowing-resistant polystyrene resin for optical plates, characterized in that: Used to prepare the yellowing-resistant polystyrene resin for optical plates as claimed in claim 1 or 2, the preparation method comprising: Performing dehydration and adsorption treatment on the styrene monomer to reduce the water content in the styrene monomer to obtain a pretreated raw material; subjecting the pretreated raw material to a prepolymerization reaction to obtain a prepolymerization product; The prepolymer product is subjected to multiple polymerization reactions to obtain a polymerization product, and in at least one polymerization reaction of the multiple polymerization reactions, the polymerization product is mixed with a styrene addition solution, wherein the styrene addition solution comprises styrene, an antioxidant, an antioxidant auxiliary, an ultraviolet absorber and a light stabilizer; Performing devolatilization and purification treatment on the polymerization product to reduce the content of the styrene monomer in the polymerization product to obtain a devolatilized material; The devolatilized material is processed to obtain the yellowing-resistant polystyrene resin for optical plates.

4. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 3, characterized in that: The step of subjecting the pretreated raw material to a prepolymerization reaction specifically comprises: The pretreated raw material is placed in a reaction vessel, and the reaction vessel is heated to 145° C. to 157° C. The reaction time is 3 h to 3.5 h, and the pretreated raw material is stirred at a speed of 19 r / min to 21 r / min.

5. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 3 or 4, characterized in that: The step of subjecting the prepolymer product to multiple polymerization reactions specifically comprises: The prepolymer product is sequentially placed in a first reactor, a second reactor and a third reactor to carry out the polymerization reaction multiple times. When the prepolymer product is undergoing the polymerization reaction in the second reactor, the styrene addition solution is placed in the second reactor. The polymerization reaction is carried out in the presence of both the lubricant and the molecular weight regulator, in the absence of both, or in the presence of one of them.

6. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 5, characterized in that: The temperature in the first reactor is 140°C to 160°C, the temperature in the second reactor is 1°C to 3°C higher than the temperature in the first reactor, and the temperature in the third reactor is 1°C to 3°C higher than the temperature in the second reactor.

7. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 3, characterized in that: The mass ratio of the prepolymer product to the lubricant is 100:(0 to 1.0); the molecular weight regulator is mineral white oil, and the mass ratio of the prepolymer product to the molecular weight regulator is 100:(0 to 5).

8. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 3, characterized in that: The devolatilization and purification treatment of the polymerization product specifically includes: The polymerization product is subjected to the devolatilization treatment at a temperature of 220° C. to 250° C. and an absolute pressure of 0.1 kPa to 8 kPa; The polymer product is purified at a temperature of 50°C to 60°C.

9. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 8, characterized in that The devolatilization treatment includes a first devolatilization treatment stage, a second devolatilization treatment stage and a third devolatilization treatment stage, wherein the temperature of the first devolatilization treatment stage is 220°C to 230°C and the absolute pressure is 0.1kPa to 0.25kPa, the temperature of the second devolatilization treatment stage is 225°C to 240°C and the absolute pressure is 7kPa to 8kPa, and the temperature of the third devolatilization treatment stage is 230°C to 250°C and the absolute pressure is 7kPa to 8kPa.

10. The method for preparing the yellowing-resistant polystyrene resin for optical plates according to claim 3, characterized in that: Before the dehydration treatment and adsorption treatment of the styrene monomer, the method further comprises: The antioxidant, the antioxidant auxiliary, the ultraviolet absorber and the light stabilizer are dissolved in the styrene to obtain the styrene addition solution.

Images