Preparation process of bi-component flame-retardant low-viscosity unsaturated polyester resin

Abstract

The invention discloses a preparation process of bi-component flame-retardant low-viscosity unsaturated polyester resin, and belongs to the technical field of polymer materials, a flame retardant is fixed by grafting a flame-retardant component trichloroethyl phosphate on the surface of a prepared core-shell ceramic heat-conducting nanosphere, and the flame-retardant core-shell ceramic heat-conducting nanosphere is obtained; the flame-retardant core-shell ceramic heat-conducting nanospheres are subjected to acrylic acid modification and are used as a cross-linking component, so that the flame-retardant core-shell ceramic heat-conducting nanospheres are cross-linked in a polymerization network of polyester resin, the mechanical property of the polyester resin is improved, and migration of flame-retardant components in the long-term use process is avoided; the shell structure of the core-shell ceramic heat-conducting nanosphere is titanium-based MOF, the subsequent flame-retardant component trichloroethyl phosphate is grafted on the shell, and the titanium-based MOF has excellent capability of catalyzing carbon formation, can quickly and stably cooperate with the trichloroethyl phosphate to play a flame-retardant role, and can effectively avoid reduction of the synergistic effect caused by steric hindrance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a preparation process of a two-component flame-retardant low-viscosity unsaturated polyester resin. Background Art

[0002] Saturated polyester resin is generally formed by the condensation of unsaturated dibasic acid diols or saturated dibasic acid unsaturated diols. It is a linear polymer compound with ester bonds and unsaturated double bonds. As a thermosetting plastic that can be cured at room temperature or high temperature, unsaturated polyester resin has excellent molding processability, low cost and good comprehensive performance. It is the most widely used matrix resin in the resin-based fiber reinforced composite material industry to date.

[0003] However, unsaturated polyester resins also present some problems during use, such as their widespread brittleness and flammability. Furthermore, during thermal decomposition, unsaturated polyester resins break their molecular chains, generating flammable gases such as styrene and polystyrene. These gases are classified as "harmful fumes," polluting the environment and significantly hindering rescue efforts. Furthermore, the escape of flammable gases creates numerous cavities in the resin, allowing air to quickly enter. The oxygen in the air accelerates the combustion and decomposition of the resin, further exacerbating the spread of fire. Therefore, it is imperative to improve the flame retardant properties of unsaturated polyester resins.

[0004] A common method is to add flame retardants to unsaturated polyester resins. Flame retardants are categorized into additive and reactive types based on their application method. Additive flame retardants are mechanically mixed into the polymer material. Examples include inorganic flame retardants such as aluminum hydroxide, magnesium hydroxide, red phosphorus, and phosphates; and organic flame retardants such as halogenated flame retardants, boron-containing flame retardants, silicon-containing flame retardants, and macromolecular intumescent flame retardants. Aluminum hydroxide powder is a relatively common additive flame retardant.

[0005] However, when aluminum hydroxide powder is added to unsaturated polyester resin, the added amount generally has to reach more than 50% of the weight of the unsaturated polyester resin, which greatly reduces the mechanical properties of the fiber-reinforced resin-based composite products prepared subsequently.

[0006] Chinese patent publication number CN112852134B discloses an additive flame-retardant unsaturated polyester resin and a preparation method thereof. In this solution, aluminum hydroxide powder and a phosphorus-containing flame retardant are used as the flame retardant main body, so that the aluminum hydroxide powder and the phosphorus-containing flame retardant cooperate with each other, so that the prepared flame-retardant unsaturated polyester resin has good flame retardant properties and does not excessively affect the mechanical properties of subsequent fiber-reinforced resin-based composite products. However, in this solution, the various raw materials and the flame retardant are only physically mixed, which easily affects the bonding with the resin and affects the overall strength.

[0007] Chinese patent publication number CN102181014B discloses a two-component flame-retardant, low-viscosity unsaturated polyester resin and its preparation method. The resin viscosity is reduced by adding a polymerization inhibitor to control the molecular weight and a cross-linking agent. Divinylbenzene is added to increase the cross-linking density and material rigidity, thereby increasing the material's strength. A flame-retardant component is introduced to achieve the flame-retardant purpose of the material. An accelerator and a curing agent are added to the unsaturated polyester resin to form components A and B, respectively, forming a stable consolidated structure. However, the flame-retardant component trichloroethyl phosphate in this solution is an additive flame retardant and is prone to precipitation or migration over time. Summary of the Invention

[0008] The present invention aims to provide a process for preparing a two-component flame-retardant, low-viscosity unsaturated polyester resin. The process comprises preparing core-shell ceramic thermally conductive nanospheres and grafting a flame-retardant component, trichloroethyl phosphate, onto the surface of the prepared nanospheres to immobilize the flame retardant. The nanospheres are then modified with acrylic acid, which serves as a crosslinking component to achieve crosslinking of the nanospheres within the polymer network of the polyester resin. This improves the mechanical properties of the polyester resin and prevents migration of the flame-retardant component during long-term use.

[0009] The purpose of the present invention can be achieved through the following technical solutions: A preparation process of a two-component flame-retardant low-viscosity unsaturated polyester resin comprises the following steps: Step 1: ceramic thermal conductive nanospheres are obtained by calcining zirconium tetrachloride and nano magnesium oxide as raw materials with phenolic resin solution.

[0010] Step 2: Using ceramic thermal conductive nanospheres as carriers, hydrothermally synthesize titanium-based MOF on the surface to obtain core-shell ceramic thermal conductive nanospheres, which are then substituted with trichloroethyl phosphate to obtain flame-retardant core-shell ceramic thermal conductive nanospheres.

[0011] Step 3: Grafting flame-retardant core-shell ceramic thermal conductive nanospheres with acrylic acid to obtain pretreated flame-retardant core-shell ceramic thermal conductive nanospheres, which are then used as a crosslinking agent in the polymerization reaction of ethylene glycol, propylene glycol, phthalic anhydride and maleic anhydride to obtain flame-retardant modified polyester resin.

[0012] Step 4: Stirring and mixing the flame-retardant modified polyester resin and cobalt isooctanoate in a mass ratio of 100-110:0.2-0.3 to obtain component A; stirring and mixing the flame-retardant modified polyester resin and methyl ethyl ketone peroxide in a mass ratio of 100-110:0.4-0.5 to obtain component B, mixing components A and B in a volume ratio of 1:1, and curing them at 20-25°C and 500-600r / min for 30-40min to obtain a two-component flame-retardant low-viscosity unsaturated polyester resin.

[0013] Furthermore, the specific preparation steps of ceramic thermal conductive nanospheres are as follows: Zirconium tetrachloride, nano-magnesium oxide and acetylacetone solution are added to a reactor, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, then ethanol is added and stirring is continued for 20-30 minutes to obtain a mixed solution; the mixed solution and phenolic resin solution are added to the reactor in a dosage ratio of 1-2L:800-900mL, stirred at 150-160°C and 500-600 r / min for 20-22 hours, filtered, the filter cake is washed with deionized water 2-4 times, vacuum dried at 60-70°C for 1-2 hours, and the product is transferred to a muffle furnace. Under nitrogen protection, the temperature is increased to 800-890°C at a rate of 5-6°C / min and kept warm for 1-2 hours, and then the temperature is increased to 1500-1600°C at a rate of 10-12°C / min and kept warm for 1-2 hours to obtain ceramic thermal conductive nanospheres.

[0014] Furthermore, the usage ratio of zirconium tetrachloride, nano-magnesium oxide, acetylacetone solution and ethanol is 200-300 g: 300-400 g: 1-2 L: 500-600 mL.

[0015] Furthermore, the specific preparation steps of the core-shell ceramic thermal conductive nanospheres are as follows: Ceramic thermally conductive nanospheres, 2,5-diaminoterephthalic acid and N,N-dimethylformamide are added to a polytetrafluoroethylene-lined autoclave, stirred at 20-25°C and 500-600 r / min for 30-40 minutes, and then a mixed solution of sodium hexadecyl sulfate and 60-70wt% ethanol solution is added, and stirring is continued for 30-40 minutes. Then, titanium tetrachloride is added, heated to 120-130°C, and the reaction is continued for 20-22 hours. The mixture is naturally cooled to room temperature and filtered. The filter cake is washed 2-4 times with methanol solution and deionized water, respectively, and vacuum dried at 60-70°C for 1-2 hours to obtain core-shell ceramic thermally conductive nanospheres.

[0016] Furthermore, the usage ratio of ceramic thermal conductive nanospheres, 2,5-diaminoterephthalic acid, N,N-dimethylformamide, sodium hexadecyl sulfate, ethanol solution and titanium tetrachloride is 150-160 g: 160-170 g: 800-900 mL: 50-60 mL: 120-130 mL: 80-90 g.

[0017] Furthermore, the specific preparation steps of the flame retardant core-shell ceramic thermal conductive nanospheres are as follows: Trichloroethyl phosphate, core-shell ceramic thermal conductive nanospheres and N,N-dimethylformamide were added to a reaction kettle, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, and then catalyst triethylamine was added. The mixture was heated to 80-90°C and stirred for 2-3 hours. The mixture was filtered, and the filter cake was washed with deionized water for 2-4 times and vacuum dried at 60-70°C for 1-2 hours to obtain flame-retardant core-shell ceramic thermal conductive nanospheres.

[0018] Furthermore, the usage ratio of trichloroethyl phosphate, core-shell ceramic thermal conductive nanospheres, N,N-dimethylformamide and triethylamine is 120-130 g: 50-60 g: 800-900 mL: 12-13 g.

[0019] Furthermore, the specific preparation steps of the pre-treated flame retardant core-shell ceramic thermal conductive nanospheres are as follows: Add flame-retardant core-shell ceramic thermal conductive nanospheres, acrylic acid and N,N-dimethylformamide into a reactor, stir for 20-30 minutes at 20-25°C and 500-600 r / min, then add catalyst triethylamine, continue stirring for 2-4 hours, filter, wash the filter cake with deionized water 2-4 times, and vacuum dry at 60-70°C for 1-2 hours to obtain pretreated flame-retardant core-shell ceramic thermal conductive nanospheres; Furthermore, the usage ratio of the flame-retardant core-shell ceramic thermal conductive nanospheres, acrylic acid, N,N-dimethylformamide and triethylamine is 120-140 g: 200-300 mL: 2-3 L: 15-18 g.

[0020] Furthermore, the specific preparation steps of the flame retardant modified polyester resin are as follows: Ethylene glycol, propylene glycol, phthalic anhydride and maleic anhydride are added to a reactor, stirred at 50-60° C. and 500-600 r / min for 20-30 min, heated to 165-170° C., and subjected to polycondensation reaction for 1-2 h. The temperature is then raised to 215-220° C. and the reaction is continued until the acid value reaches 70-75 mg KOH / g. Hydroquinone as a polymerization inhibitor is added, the temperature is lowered to 135-140° C., and then pretreated flame-retardant core-shell ceramic thermal conductive nanospheres are added. The reaction is continued for 1-2 h, filtered, and the precipitate is washed 2-4 times with deionized water and anhydrous ethanol, and vacuum dried at 60-70° C. for 1-2 h to obtain a flame-retardant modified polyester resin.

[0021] Furthermore, the usage ratio of ethylene glycol, propylene glycol, phthalic anhydride, maleic anhydride, hydroquinone and pretreated flame-retardant core-shell ceramic thermal conductive nanospheres is 300-400g: 300-400g: 200-300g: 220-250g: 12-14g: 300-400g.

[0022] Beneficial effects of the present invention: 1. The two-component flame-retardant, low-viscosity unsaturated polyester resin prepared by the present invention comprises core-shell ceramic thermally conductive nanospheres, onto which the flame retardant trichloroethyl phosphate is grafted to fix the flame retardant, thereby obtaining flame-retardant core-shell ceramic thermally conductive nanospheres. The flame-retardant core-shell ceramic thermally conductive nanospheres are then modified with acrylic acid, which serves as a crosslinking component to achieve crosslinking of the flame-retardant core-shell ceramic thermally conductive nanospheres within the polymer network of the polyester resin, thereby improving the mechanical properties of the polyester resin and preventing the migration of the flame retardant component during long-term use.

[0023] 2. The core-shell ceramic thermally conductive nanospheres of the present invention have a unique core-shell structure that allows the polyester resin to disperse stress through slip, thereby improving the mechanical strength of the polyester resin. Furthermore, the shell structure of the core-shell ceramic thermally conductive nanospheres is a titanium-based MOF. Since the subsequent flame retardant component, trichloroethyl phosphate, is grafted onto the shell, the titanium-based MOF has excellent catalytic carbonization ability and can quickly and stably cooperate with trichloroethyl phosphate to exert a flame retardant effect, effectively avoiding the reduction of synergistic effects caused by steric hindrance. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 making creative efforts are within the scope of protection of the present invention.

[0025] Example 1: A process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin, comprising the following steps: S1: Add 200g zirconium tetrachloride, 300g nano-magnesium oxide and 1L acetylacetone solution into a reactor, stir at 20℃ and 500r / min for 20min, then add 500mL ethanol and continue stirring for 20min to obtain a mixed solution; add 1L mixed solution and 800mL phenolic resin solution into a reactor, stir at 150℃ and 500r / min for 20h, filter, wash the filter cake with deionized water twice, vacuum dry at 60℃ for 1h, transfer the product to a muffle furnace, and under nitrogen protection, heat to 800℃ at a rate of 5℃ / min and keep warm for 1h, then heat to 1500℃ at a rate of 10℃ / min and keep warm for 1h to obtain ceramic thermal conductive nanospheres.

[0026] S2: 150g of ceramic thermal conductive nanospheres, 160g of 2,5-diaminoterephthalic acid and 800mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave, stirred at 20°C and 500r / min for 30min, then a mixed solution of 50mL of sodium hexadecyl sulfate and 120mL of 60wt% ethanol solution was added, and stirring was continued for 30min. Then, 80g of titanium tetrachloride was added, heated to 120°C, and the reaction was continued for 20h. The mixture was naturally cooled to room temperature, filtered, and the filter cake was washed twice with methanol solution and deionized water respectively, and vacuum dried at 60°C for 1h to obtain core-shell ceramic thermal conductive nanospheres.

[0027] S3: 120 g of trichloroethyl phosphate, 50 g of core-shell ceramic thermal conductive nanospheres and 800 mL of N,N-dimethylformamide were added to a reactor, stirred at 20°C and 500 r / min for 20 min, then 12 g of catalyst triethylamine was added, heated to 80°C, and stirred for 2 h. The mixture was filtered, and the filter cake was washed twice with deionized water and vacuum dried at 60°C for 1 h to obtain flame-retardant core-shell ceramic thermal conductive nanospheres.

[0028] S4: 120 g of flame-retardant core-shell ceramic thermal conductive nanospheres, 200 mL of acrylic acid and 2 L of N,N-dimethylformamide were added to a reactor, stirred at 20°C and 500 r / min for 20 min, then 15 g of catalyst triethylamine was added, and stirring was continued for 2 h. The mixture was filtered, and the filter cake was washed twice with deionized water and vacuum dried at 60°C for 1 h to obtain pretreated flame-retardant core-shell ceramic thermal conductive nanospheres.

[0029] S5: Add 300 g of ethylene glycol, 300 g of propylene glycol, 200 g of phthalic anhydride and 220 g of maleic anhydride into a reactor, stir at 50°C and 500 r / min for 20 min, heat to 165°C, and carry out polycondensation reaction for 1 h. Continue to heat to 215°C and continue to react until the acid value reaches 70 mg KOH / g. Add 12 g of polymerization inhibitor hydroquinone, cool to 135°C, and then add 300 g of pretreated flame-retardant core-shell ceramic thermal conductive nanospheres. Continue to react for 1 h, filter, wash the precipitate twice with deionized water and anhydrous ethanol, and dry in vacuo at 60°C for 1 h to obtain a flame-retardant modified polyester resin.

[0030] S6: 100 g of flame-retardant modified polyester resin and 0.2 g of cobalt isooctanoate are stirred and mixed to obtain component A; 100 g of flame-retardant modified polyester resin and 0.4 g of methyl ethyl ketone peroxide are stirred and mixed to obtain component B, components A and B are mixed in a volume ratio of 1:1, and cured at 20°C and 500 r / min for 30 min to obtain a two-component flame-retardant low-viscosity unsaturated polyester resin.

[0031] Example 2: A process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin, comprising the following steps: S1: 250g zirconium tetrachloride, 350g nano-magnesium oxide and 1.5L acetylacetone solution were added to a reactor, stirred at 22.5℃ and 550r / min for 25min, then 550mL ethanol was added and stirring was continued for 25min to obtain a mixed solution; 1.5L mixed solution and 850mL phenolic resin solution were added to a reactor, stirred at 155℃ and 550r / min for 21h, filtered, and the filter cake was washed with deionized water 3 times, vacuum dried at 65℃ for 1.5h, and the product was transferred to a muffle furnace. Under nitrogen protection, the temperature was increased to 845℃ at a rate of 5.5℃ / min and kept warm for 1.5h, and then the temperature was increased to 1550℃ at a rate of 11℃ / min and kept warm for 1.5h to obtain ceramic thermal conductive nanospheres.

[0032] S2: 155g of ceramic thermal conductive nanospheres, 165g of 2,5-diaminoterephthalic acid and 850mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave, stirred at 22.5°C and 550r / min for 35min, and then a mixed solution of 55mL of sodium hexadecyl sulfate and 125mL of 65wt% ethanol solution was added, and stirring was continued for 35min. Then, 85g of titanium tetrachloride was added, heated to 125°C, and the reaction was continued for 21h. The mixture was naturally cooled to room temperature and filtered. The filter cake was washed three times with methanol solution and deionized water respectively, and vacuum dried at 65°C for 1.5h to obtain core-shell ceramic thermal conductive nanospheres.

[0033] S3: 125 g of trichloroethyl phosphate, 55 g of core-shell ceramic thermal conductive nanospheres and 850 mL of N,N-dimethylformamide were added to a reactor, stirred at 22.5°C and 550 r / min for 25 min, then 12.5 g of catalyst triethylamine was added, heated to 85°C, and stirred for 2.5 h. The mixture was filtered, and the filter cake was washed three times with deionized water and vacuum dried at 65°C for 1.5 h to obtain flame-retardant core-shell ceramic thermal conductive nanospheres.

[0034] S4: 130 g of flame-retardant core-shell ceramic thermally conductive nanospheres, 250 mL of acrylic acid and 2.5 L of N,N-dimethylformamide were added to the reactor, stirred at 22.5 ° C and 550 r / min for 25 min, and then 16.5 g of catalyst triethylamine was added, and stirring was continued for 3 h. The mixture was filtered, and the filter cake was washed with deionized water 3 times and vacuum dried at 65 ° C for 1.5 h to obtain pretreated flame-retardant core-shell ceramic thermally conductive nanospheres.

[0035] S5: Add 350g of ethylene glycol, 350g of propylene glycol, 250g of phthalic anhydride and 235g of maleic anhydride into a reactor, stir at 55°C and 550r / min for 25min, heat to 167.5°C, and carry out polycondensation reaction for 1.5h. Continue to heat to 217.5°C and continue to react until the acid value reaches 72.5mg KOH / g. Add 13g of polymerization inhibitor hydroquinone, cool to 137.5°C, and then add 350g of pretreated flame-retardant core-shell ceramic thermal conductive nanospheres. Continue to react for 1.5h, filter, wash the precipitate with deionized water and anhydrous ethanol three times, and dry in vacuo at 65°C for 1.5h to obtain a flame-retardant modified polyester resin.

[0036] S6: 105 g of flame-retardant modified polyester resin and 0.25 g of cobalt isooctanoate were stirred and mixed to obtain component A; 105 g of flame-retardant modified polyester resin and 0.45 g of methyl ethyl ketone peroxide were stirred and mixed to obtain component B, components A and B were mixed in a volume ratio of 1:1, and cured at 22.5°C and 550 r / min for 35 min to obtain a two-component flame-retardant low-viscosity unsaturated polyester resin.

[0037] Example 3: A process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin, comprising the following steps: S1: 300g zirconium tetrachloride, 400g nano-magnesium oxide and 2L acetylacetone solution were added to a reactor, stirred at 25°C and 600r / min for 30min, then 600mL ethanol was added and stirring was continued for 30min to obtain a mixed solution; 2L mixed solution and 900mL phenolic resin solution were added to a reactor, stirred at 160°C and 600r / min for 22h, filtered, and the filter cake was washed with deionized water 4 times, vacuum dried at 70°C for 2h, and the product was transferred to a muffle furnace. Under nitrogen protection, the temperature was increased to 890°C at a rate of 6°C / min and kept warm for 2h, and then the temperature was increased to 1600°C at a rate of 12°C / min and kept warm for 2h to obtain ceramic thermal conductive nanospheres.

[0038] S2: 160g of ceramic thermal conductive nanospheres, 170g of 2,5-diaminoterephthalic acid and 900mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave, stirred at 25°C and 600r / min for 40min, then a mixed solution of 60mL of sodium hexadecyl sulfate and 130mL of 70wt% ethanol solution was added, and stirring was continued for 40min. Then, 90g of titanium tetrachloride was added, heated to 130°C, and the reaction was continued for 22h. The mixture was naturally cooled to room temperature, filtered, and the filter cake was washed 4 times with methanol solution and deionized water respectively, and vacuum dried at 70°C for 2h to obtain core-shell ceramic thermal conductive nanospheres.

[0039] S3: 130 g of trichloroethyl phosphate, 60 g of core-shell ceramic thermal conductive nanospheres and 900 mL of N,N-dimethylformamide were added to a reactor, stirred at 25°C and 600 r / min for 30 min, then 13 g of catalyst triethylamine was added, heated to 90°C, and stirred for 3 h. The mixture was filtered, and the filter cake was washed four times with deionized water and vacuum dried at 70°C for 2 h to obtain flame-retardant core-shell ceramic thermal conductive nanospheres.

[0040] S4: 140 g of flame-retardant core-shell ceramic thermal conductive nanospheres, 300 mL of acrylic acid and 3 L of N,N-dimethylformamide were added to the reactor, stirred at 25°C and 600 r / min for 30 min, then 18 g of catalyst triethylamine was added, and stirring was continued for 4 h. The mixture was filtered, and the filter cake was washed with deionized water 4 times and vacuum dried at 70°C for 2 h to obtain pretreated flame-retardant core-shell ceramic thermal conductive nanospheres.

[0041] S5: Add 400 g of ethylene glycol, 400 g of propylene glycol, 300 g of phthalic anhydride and 250 g of maleic anhydride into a reactor, stir at 60°C and 600 r / min for 30 min, heat to 170°C, and carry out polycondensation reaction for 2 h. Continue to heat to 220°C and continue to react until the acid value reaches 75 mg KOH / g. Add 14 g of polymerization inhibitor hydroquinone, cool to 140°C, and then add 400 g of pretreated flame-retardant core-shell ceramic thermal conductive nanospheres. Continue to react for 2 h, filter, wash the precipitate with deionized water and anhydrous ethanol 4 times, and dry in vacuo at 70°C for 2 h to obtain a flame-retardant modified polyester resin.

[0042] S6: 110 g of flame-retardant modified polyester resin and 0.3 g of cobalt isooctanoate were stirred and mixed to obtain component A; 110 g of flame-retardant modified polyester resin and 0.5 g of methyl ethyl ketone peroxide were stirred and mixed to obtain component B, components A and B were mixed in a volume ratio of 1:1, and cured at 25°C and 600 r / min for 40 min to obtain a two-component flame-retardant low-viscosity unsaturated polyester resin.

[0043] Comparative Example 1: Based on Example 3, the core-shell ceramic thermally conductive nanospheres in step S3 are replaced by the ceramic thermally conductive nanospheres in step S1.

[0044] Comparative Example 2: Based on Example 3, without step S3, the flame retardant core-shell ceramic thermally conductive nanospheres in step S4 are replaced by the stirred mixture of core-shell ceramic thermally conductive nanospheres and trichloroethyl phosphate in step S2.

[0045] Comparative Example 3: Based on Example 3, without step S4, the pretreated flame-retardant core-shell ceramic thermally conductive nanospheres in step S5 are replaced by the flame-retardant core-shell ceramic thermally conductive nanospheres in step S3.

[0046] The performance of the two-component flame-retardant low-viscosity unsaturated polyester resins prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested. The unsaturated polyester resin was impregnated into glass fiber yarn and pultruded to obtain samples with a length of 1500 mm and a width of 150 mm. The flame growth index (FSI) and smoke growth index (SDI) of the samples were tested according to ASTM E84-15 "Standard Test Method for Surface Burning Characteristics of Building Materials". The tensile strength of the samples was tested according to GB / T 1447-2005 "Test Method for Tensile Properties of Fiber Reinforced Plastics". The samples were placed in an environment of 85°C / 85% relative humidity for 1000 hours and then repeated. The results are shown in Table 1: Table 1 Unsaturated polyester resin performance test results

[0047] It can be seen from Table 1 that the two-component flame-retardant low-viscosity unsaturated polyester resins prepared in Examples 1 to 3 have good flame retardancy, low viscosity, high strength, and the flame retardant component is not easy to migrate during long-term use.

[0048] The core-shell ceramic thermally conductive nanospheres in Comparative Example 1 are replaced by the ceramic thermally conductive nanospheres in step S1, which are not coated with a MOF shell. Trichloroethyl phosphate is directly physically adsorbed on the surface of the ceramic balls. After long-term use, the flame retardant is easily precipitated. The loss of the MOF shell weakens the slip ability of the interface between the ceramic balls and the resin, resulting in uneven stress transfer and decreased tensile strength. The titanium-based MOF shell is the key to catalytic carbonization, and its flame retardant synergistic effect is weakened after its loss.

[0049] The flame-retardant core-shell ceramic thermally conductive nanospheres in Comparative Example 2 are replaced by a stirred mixture of core-shell ceramic thermally conductive nanospheres and trichloroethyl phosphate in step S2. The trichloroethyl phosphate is not chemically grafted but only physically mixed. After heating, it easily migrates to the resin surface and volatilizes. The ungrafted flame retardant forms a weak interface in the resin, becoming a crack source, reducing the tensile strength, and the physically mixed flame retardant seeps out with the solvent, and the flame retardant performance decays over time.

[0050] The pretreated flame-retardant core-shell ceramic thermally conductive nanospheres in Comparative Example 3 were replaced with the flame-retardant core-shell ceramic thermally conductive nanospheres in step S3. No double bonds were introduced on the surface of the nanospheres by acrylic acid, resulting in their inability to participate in the polyester resin cross-linking network and a decrease in tensile strength.

[0051] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin, characterized in that: The steps include: S1: Ceramic thermal conductive nanospheres are obtained by calcining zirconium tetrachloride and nano-magnesium oxide with phenolic resin solution; S2: Using ceramic thermal conductive nanospheres as carriers, titanium-based MOF is hydrothermally synthesized on the surface to obtain core-shell ceramic thermal conductive nanospheres, which are then substituted with trichloroethyl phosphate to obtain flame-retardant core-shell ceramic thermal conductive nanospheres; S3: Pretreated flame-retardant core-shell ceramic thermally conductive nanospheres are obtained by grafting flame-retardant core-shell ceramic thermally conductive nanospheres with acrylic acid, and then used as a crosslinking agent in the polymerization reaction of ethylene glycol, propylene glycol, phthalic anhydride and maleic anhydride to obtain a flame-retardant modified polyester resin; S4: mixing the flame retardant modified polyester resin and cobalt isooctanoate in a certain mass ratio to obtain component A; The flame retardant modified polyester resin and methyl ethyl ketone peroxide are mixed and stirred in a certain mass ratio range to obtain component B, and the A and B components are mixed in a volume ratio of 1:1 and cured to obtain a two-component flame retardant low-viscosity unsaturated polyester resin.

2. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 1, characterized in that: The specific preparation steps of the ceramic thermal conductive nanospheres are as follows: Zirconium tetrachloride, nano-magnesium oxide and acetylacetone solution are added to a reactor, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, then ethanol is added and stirring is continued for 20-30 minutes to obtain a mixed solution; the mixed solution and phenolic resin solution are added to the reactor in a dosage ratio of 1-2L:800-900mL, stirred at 150-160°C and 500-600 r / min for 20-22 hours, filtered, the filter cake is washed with deionized water 2-4 times, vacuum dried at 60-70°C for 1-2 hours, and the product is transferred to a muffle furnace. Under nitrogen protection, the temperature is increased to 800-890°C at a rate of 5-6°C / min and kept warm for 1-2 hours, and then the temperature is increased to 1500-1600°C at a rate of 10-12°C / min and kept warm for 1-2 hours to obtain ceramic thermal conductive nanospheres.

3. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 2, characterized in that: The usage ratio of the zirconium tetrachloride, nano-magnesium oxide, acetylacetone solution and ethanol is 200-300 g: 300-400 g: 1-2 L: 500-600 mL.

4. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 1, characterized in that: The specific preparation steps of the core-shell ceramic thermal conductive nanospheres are as follows: Ceramic thermally conductive nanospheres, 2,5-diaminoterephthalic acid and N,N-dimethylformamide are added to a polytetrafluoroethylene-lined autoclave, stirred at 20-25°C and 500-600 r / min for 30-40 minutes, then a mixed solution of sodium hexadecyl sulfate and 60-70wt% ethanol solution is added, and stirring is continued for 30-40 minutes. Then, titanium tetrachloride is added, heated to 120-130°C, and the reaction is continued for 20-22 hours. The mixture is naturally cooled, filtered, washed, and vacuum dried to obtain core-shell ceramic thermally conductive nanospheres.

5. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 4, characterized in that: The usage ratio of the ceramic thermal conductive nanospheres, 2,5-diaminoterephthalic acid, N,N-dimethylformamide, sodium hexadecyl sulfate, ethanol solution and titanium tetrachloride is 150-160 g: 160-170 g: 800-900 mL: 50-60 mL: 120-130 mL: 80-90 g.

6. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 1, characterized in that: The specific preparation steps of the flame retardant core-shell ceramic thermal conductive nanospheres are as follows: Trichloroethyl phosphate, core-shell ceramic thermal conductive nanospheres and N,N-dimethylformamide were added to a reaction kettle, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, and then triethylamine was added. The mixture was heated to 80-90°C and stirred for 2-3 hours. The mixture was filtered, washed and vacuum dried to obtain flame-retardant core-shell ceramic thermal conductive nanospheres. The usage ratio of the trichloroethyl phosphate, the core-shell ceramic thermal conductive nanospheres, N,N-dimethylformamide and triethylamine is 120-130 g: 50-60 g: 800-900 mL: 12-13 g.

7. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 1, characterized in that: The specific preparation steps of the pretreated flame-retardant core-shell ceramic thermally conductive nanospheres are as follows: Flame-retardant core-shell ceramic thermally conductive nanospheres, acrylic acid and N,N-dimethylformamide were added into a reactor, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, and then triethylamine was added. The mixture was stirred for 2-4 hours, filtered, washed and vacuum dried to obtain pretreated flame-retardant core-shell ceramic thermally conductive nanospheres.

8. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 7, characterized in that: The usage ratio of the flame-retardant core-shell ceramic thermal conductive nanospheres, acrylic acid, N,N-dimethylformamide and triethylamine is 120-140 g: 200-300 mL: 2-3 L: 15-18 g.

9. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 1, characterized in that: The specific preparation steps of the flame retardant modified polyester resin are as follows: Ethylene glycol, propylene glycol, phthalic anhydride and maleic anhydride are added to a reaction kettle, stirred at 50-60° C. and 500-600 r / min for 20-30 min, heated to 165-170° C., and subjected to polycondensation reaction for 1-2 h. The temperature is further raised to 215-220° C. and the reaction is continued until the acid value reaches 70-75 mg KOH / g. Hydroquinone is added, the temperature is lowered to 135-140° C., and then pretreated flame-retardant core-shell ceramic thermal conductive nanospheres are added. The reaction is continued for 1-2 h. The reaction is filtered, washed, and vacuum dried to obtain a flame-retardant modified polyester resin.

10. The process for preparing a two-component flame-retardant low-viscosity unsaturated polyester resin according to claim 9, characterized in that: The usage ratio of the ethylene glycol, propylene glycol, phthalic anhydride, maleic anhydride, hydroquinone and pretreated flame-retardant core-shell ceramic thermal conductive nanospheres is 300-400g: 300-400g: 200-300g: 220-250g: 12-14g: 300-400g.

Images