Flame-retardant engineering plastic as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of flame-retardant engineering plastics, and particularly relates to a flame-retardant engineering plastic as well as a preparation method and application thereof. The flame-retardant engineering plastic is prepared from the following raw materials in parts by weight: 200 parts of terephthalic acid, 100 to 150 parts of ethylene glycol, 160 to 200 parts of butanediol, 30 to 50 parts of composite porous microspheres, 150 to 200 parts of magnesium hydroxide microcapsules, 5 to 8 parts of PET (Polyethylene Terephthalate) resin and 5 to 8 parts of PBT (Polybutylene Terephthalate) resin. According to the flame-retardant engineering plastic disclosed by the invention, in the raw materials, terephthalic acid, ethylene glycol and butanediol are respectively polymerized into PET and PBT; the composite porous microspheres not only improve the flame retardance of the flame-retardant engineering plastic, but also can be used as a catalyst to catalyze esterification reaction of terephthalic acid, ethylene glycol and butanediol; magnesium hydroxide is uniformly dispersed in the flame-retardant engineering plastic through a microcapsule structure, so that the flame-retardant engineering plastic has excellent smoke suppression performance, and the PET resin and the PBT resin promote polymerization reaction of terephthalic acid, ethylene glycol and butanediol.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant engineering plastic preparation technology, specifically relating to a flame-retardant engineering plastic, its preparation method, and its application. Background Technology

[0002] Flame-retardant engineering plastics are high-performance polymer materials that significantly delay combustion and suppress flame spread while retaining the mechanical, thermal, and electrical properties of engineering plastics. Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are widely used as flame-retardant engineering plastics due to their molecular structure characteristics and modification potential.

[0003] Existing PET and PBT-based engineering plastics generally have flame retardants added to them to improve their flame retardant properties. Common flame retardants include halogenated flame retardants (such as decabromodiphenyl ether), phosphorus-based flame retardants (such as red phosphorus and ammonium polyphosphate), nitrogen-based flame retardants (melamine and its derivatives), inorganic flame retardants (metal hydroxides), and silicone-based flame retardants (organosilicon resins).

[0004] However, the addition of flame retardants (such as bromine-based, phosphorus-based, and inorganic ones) has poor compatibility with the matrix (PET, PBT) and uneven mixing, resulting in multiple stress concentration points. Ultimately, this disrupts the regularity of the molecular chains, causing engineering plastics to have improved flame retardant properties to some extent, but their tensile strength and impact strength will also be significantly reduced. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a flame-retardant engineering plastic, its preparation method, and its applications. This solves at least one aspect of the above-mentioned technical problems.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a flame-retardant engineering plastic comprising the following parts by weight of raw materials: 200 parts terephthalic acid, 100-150 parts ethylene glycol, 160-200 parts butylene glycol, 30-50 parts composite porous microspheres, 150-200 parts magnesium hydroxide microcapsules, 5-8 parts PET resin, and 5-8 parts PBT resin.

[0007] Secondly, the present invention provides a method for preparing flame-retardant engineering plastics, comprising the following steps: The raw material mixture is melt-extruded after being reacted at a constant temperature. The raw material mixture contains terephthalic acid, ethylene glycol, butanediol, composite porous microspheres, magnesium hydroxide microcapsules, PET resin, and PBT resin.

[0008] Thirdly, the present invention provides an application of flame-retardant engineering plastics in the field of pipes.

[0009] The flame-retardant engineering plastic and its preparation method provided by this invention have at least the following beneficial technical effects compared with the prior art: (1) In the flame-retardant engineering plastic of the present invention, terephthalic acid is polymerized with ethylene glycol and butanediol to form PET and PBT respectively; the composite porous microspheres not only improve the flame retardancy of the flame-retardant engineering plastic, but also act as a catalyst to catalyze the esterification reaction of terephthalic acid with ethylene glycol and butanediol, and also act as a carrier to graft polymerized PET and PBT on its surface. The generated PET and PBT are also interspersed in the pores of the composite porous microspheres, thereby improving the uniformity of the material and thus improving the structural stability of the flame-retardant engineering plastic; magnesium hydroxide is uniformly dispersed in the flame-retardant engineering plastic through the microcapsule structure, thereby giving the flame-retardant engineering plastic excellent smoke suppression performance; PET resin and PBT resin promote the polymerization reaction of terephthalic acid with ethylene glycol and butanediol.

[0010] (2) The method for preparing the flame-retardant engineering plastic of the present invention involves in-situ polymerization of terephthalic acid, ethylene glycol and butanediol and intercalation in the pores of the composite porous microspheres to improve the flame retardancy and structural stability of the flame-retardant engineering plastic. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0012] Obviously, the following description is merely some examples or embodiments of the present invention. Those skilled in the art can apply the present invention to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, modifications to design, manufacturing, or production based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the present invention.

[0013] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the invention and is not intended to limit the subject matter of the claims.

[0014] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0015] The first aspect of this invention provides a flame-retardant engineering plastic, comprising the following parts by weight of raw materials: 200 parts terephthalic acid, 100-150 parts ethylene glycol, 160-200 parts butylene glycol, 30-50 parts composite porous microspheres, 150-200 parts magnesium hydroxide microcapsules, 5-8 parts PET resin, and 5-8 parts PBT resin.

[0016] In the raw materials of the flame-retardant engineering plastic provided by this invention, terephthalic acid is polymerized with ethylene glycol and butanediol to form PET and PBT, respectively; the composite porous microspheres not only improve the flame retardancy of the flame-retardant engineering plastic, but also serve as a carrier for grafting polymerized PET and PBT onto its surface, thereby improving the structural stability of the flame-retardant engineering plastic; magnesium hydroxide is uniformly dispersed in the flame-retardant engineering plastic through a microcapsule structure, thereby giving the flame-retardant engineering plastic excellent smoke suppression performance; PET resin and PBT resin can promote the polymerization reaction of terephthalic acid with ethylene glycol and butanediol.

[0017] In some embodiments, the average particle size of terephthalic acid is 10 μm to 20 μm.

[0018] In some embodiments, the composite porous microspheres are alumina-modified silica porous microspheres.

[0019] In some embodiments, the silicon-to-aluminum molar ratio in the alumina-modified silica porous microspheres is (50~70):1. In this case, the high specific surface area of ​​the silica porous microspheres is retained, while the weak acidity of alumina improves the grafting ability of the porous microspheres.

[0020] In some embodiments, the core material of the magnesium hydroxide microcapsules is nano-magnesium hydroxide, and the shell material is polycarbonate. In this case, the shell material is polycarbonate, and the melting point of polycarbonate is close to that of PET resin and PBT resin, allowing for simultaneous melting. Furthermore, the polycarbonate is dispersed in the form of the shell material, which can improve the uniformity of polycarbonate in flame-retardant engineering plastics, thereby significantly improving the impact resistance of flame-retardant engineering plastics.

[0021] In some embodiments, the CAS number of polycarbonate is 25037-45-0 (melting point 220ºC~230ºC).

[0022] In some embodiments, the average particle size of the magnesium hydroxide microcapsules is 20 μm to 40 μm.

[0023] In some embodiments, the average particle size of nano-magnesium hydroxide is 100 nm to 200 nm.

[0024] In some embodiments, the CAS number of PET (polyethylene terephthalate) resin is 25038-59-9 (melting point 250ºC~255ºC).

[0025] In some embodiments, the average particle size of the PET resin is 10 μm to 30 μm.

[0026] In some embodiments, the CAS number of PBT (polybutylene terephthalate) resin is 26062-94-2 (melting point 226ºC).

[0027] In some embodiments, the average particle size of the PBT resin is 10 μm to 30 μm.

[0028] A second aspect of this invention provides a method for preparing flame-retardant engineering plastics, comprising the following steps: S10. The raw material mixture is melt-extruded after being reacted at a constant temperature. The raw material mixture contains terephthalic acid, ethylene glycol, butanediol, composite porous microspheres, magnesium hydroxide microcapsules, PET resin, and PBT resin.

[0029] The method for preparing flame-retardant engineering plastics provided in this invention involves in-situ polymerization of terephthalic acid, ethylene glycol, and butanediol in the raw material mixture during a constant-temperature reaction. These components are then interspersed within the pores of the composite porous microspheres, improving the uniformity of the system components and thus enhancing the flame-retardant performance of the flame-retardant engineering plastics. Furthermore, the melting of the shell material of the magnesium hydroxide microcapsules releases magnesium hydroxide, and the constant-temperature reaction improves the structural stability of the flame-retardant engineering plastics.

[0030] In some embodiments, the preparation of the raw material mixture in step S10 above includes the following steps: S101. After acidification treatment, the composite porous microspheres are mixed with the suspension; The suspension contains terephthalic acid, ethylene glycol, butanediol, magnesium hydroxide microcapsules, PET resin, and PBT resin.

[0031] In some embodiments, the preparation of the suspension in step S101 above includes the following steps: S1011. Under stirring conditions of 10 rpm to 30 rpm, terephthalic acid, PBT resin, PET resin and magnesium hydroxide microcapsules were dispersed into a mixed alcohol solution of ethylene glycol and butanediol.

[0032] In the preparation of the above suspension, the suspension is prepared by stirring at a speed of 10 rpm to 30 rpm, which can mix the suspension evenly without damaging the structure of PBT resin, PET resin and magnesium hydroxide microcapsules.

[0033] In some embodiments, in step S101 above, the acidification step includes: S1012. The composite porous microspheres and 3-mercaptopropyltrimethoxysilane were mixed and refluxed in anhydrous toluene to obtain thiolized composite porous microspheres.

[0034] S1013. Oxidize the thiolized composite porous microspheres with an oxidizing agent to obtain acidified composite porous microspheres.

[0035] In the above acidification process, thiol groups are first introduced onto the surface of the composite porous microspheres using a silane coupling agent containing acidic groups, and then the thiol groups are oxidized into sulfonic acid groups. The strongly acidic composite porous microspheres can catalyze the esterification reaction between terephthalic acid and ethylene glycol and butanediol, avoiding the introduction of additional catalysts to form impurities.

[0036] In some embodiments, in step S1012 above, the solid-liquid ratio of the composite porous microspheres and 3-mercaptopropyltrimethoxysilane is 1 g:(10 ml~20 ml). In some embodiments, in step S1012 above, the reflux reaction temperature is 110°C~120°C. In some embodiments, in step S1012 above, the reflux reaction time is 8 h~10 h. In this case, the thiol groups can be sufficiently grafted onto the composite porous microspheres, ensuring the grafting rate of the thiol groups and the structural integrity of the porous microspheres.

[0037] In some embodiments, in step S1013 above, the oxidant includes at least one of hydrogen peroxide and dilute nitric acid.

[0038] In some embodiments, the concentration of dilute nitric acid is 30% to 40%. In this case, dilute nitric acid can oxidize thiol groups to sulfonic acid groups without damaging the microsphere structure.

[0039] In some embodiments, in step S1013 above, the solid-liquid ratio of the thiolized composite porous microspheres to the oxidant is 1 g: (10 ml ~ 20 ml).

[0040] In some embodiments, in step S1013 above, the step of oxidizing the thiol-modified composite porous microspheres with an oxidant includes: S10131. Under stirring conditions of 100 rpm to 200 rpm, the oxidant and the thiolized composite porous microspheres are mixed and oxidized.

[0041] In some embodiments, in step S10131 above, the temperature of the mixed oxidation is 70°C to 80°C. In some embodiments, in step S10131 above, the time of the mixed oxidation is 7h to 8h.

[0042] In some embodiments, the step of mixing the composite porous microspheres with the suspension after acidification treatment in step S101 above includes: S1014. Under stirring conditions of 10 rpm to 30 rpm, the acidified composite porous microspheres are added to the suspension in portions, with each addition being 5% to 10% of the total amount of acidified composite porous microspheres.

[0043] In some embodiments, the isothermal reaction step in step S10 above includes: S102. The raw material mixture is subjected to the first esterification stage, the first polycondensation stage, the second esterification stage, and the second polycondensation stage in sequence.

[0044] In some embodiments, in step S102 above, the first esterification stage includes: S1021. Under stirring conditions at 100 rpm to 200 rpm, the raw material mixture is heated to 220°C to 230°C at a heating rate of 20°C / min to 40°C / min, and then subjected to the first esterification and heat preservation.

[0045] In the above esterification stage, heating the raw material mixture to 220℃~230℃ at 20℃ / min~40℃ / min and holding it for the first esterification can preliminarily esterify terephthalic acid and butanediol.

[0046] In some embodiments, in step S1021 above, the first esterification holding time is 3h~4h.

[0047] In some embodiments, in step S102 above, the first polycondensation stage includes: S1022. Under stirring conditions at a speed of 50 rpm to 70 rpm, the raw material mixture is heated from 220℃ to 230℃ to 240℃ to 250℃ at a heating rate of 3℃ / min to 5℃ / min, and then subjected to the first polycondensation and heat preservation.

[0048] In some embodiments, in step S1022 above, the first polycondensation heat preservation time is 1h to 2h.

[0049] In some embodiments, in step S102 above, the second esterification stage includes: S1023. Under stirring conditions at 100 rpm to 200 rpm, the raw material mixture is heated from 240℃ to 250℃ to 255℃ to 260℃ at a heating rate of 8℃ / min to 10℃ / min, and then subjected to a second esterification and heat preservation.

[0050] In the above esterification stage, heating the raw material mixture from 240℃~250℃ to 255℃~260℃ at a rate of 8℃ / min~10℃ / min and holding it at this temperature for a second esterification can preliminarily esterify terephthalic acid and ethylene glycol.

[0051] In some embodiments, in step S1023 above, the second esterification holding time is 3h~4h.

[0052] In some embodiments, in step S102 above, the second polycondensation stage includes: S1024. Under stirring conditions at a speed of 50 rpm to 70 rpm, the raw material mixture is heated from 255 ℃ to 260 ℃ to 270 ℃ to 290 ℃ at a heating rate of 3 ℃ / min to 5 ℃ / min, and then subjected to a second polycondensation and heat preservation.

[0053] In some embodiments, in step S1024 above, the second polycondensation insulation time is 1h to 2h.

[0054] In some embodiments, in step S10 above, the temperature of melt extrusion is 250°C to 260°C.

[0055] The following description, in conjunction with specific embodiments, provides further details. For ease of illustration, in the following embodiments and comparative examples, 1. Engineering plastic raw materials involved: (1) The average particle size of terephthalic acid is 10 μm.

[0056] (2) The composite porous microspheres are alumina-modified silica porous microspheres with a silica-alumina molar ratio of 50:1.

[0057] (3) The average particle size of the magnesium hydroxide microcapsules is 30 μm.

[0058] (4) In the magnesium hydroxide microcapsules, the core material is nano magnesium hydroxide and the shell material is polycarbonate. The CAS number of polycarbonate is 25037-45-0.

[0059] (5) The CAS number of the PET resin is 25038-59-9, and the average particle size is 20μm.

[0060] (6) The CAS number of PBT resin is 26062-94-2, and the average particle size is 20μm.

[0061] 2. Among the preparation methods involved: (1) All composite porous microspheres were calcined at 150°C for 2 hours before acidification to ensure that the moisture in the composite porous microspheres was fully removed.

[0062] (2) Preparation of the suspension in the examples: Terephthalic acid, PBT resin, PET resin and magnesium hydroxide microcapsules were dispersed in a mixed alcohol solution of ethylene glycol and butanediol under stirring at 20 rpm.

[0063] Example 1 Example 1 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: 200 parts terephthalic acid, 100 parts ethylene glycol, 160 parts butylene glycol, 40 parts composite porous microspheres, 150 parts magnesium hydroxide microcapsules, 5 parts PET resin, and 7 parts PBT resin.

[0064] This embodiment also provides a method for preparing flame-retardant engineering plastics, the steps of which are as follows: E1. Acidification treatment E1-1. The composite porous microspheres and 3-mercaptopropyltrimethoxysilane were mixed and refluxed in anhydrous toluene to obtain thiolized composite porous microspheres; wherein the solid-liquid ratio of the composite porous microspheres and 3-mercaptopropyltrimethoxysilane was 1g:15ml, the reflux reaction temperature was 110℃, and the reflux reaction time was 8h.

[0065] E1-2. Under stirring at 100 rpm, the thiolized composite porous microspheres were oxidized with 30% dilute nitric acid to obtain acidified composite porous microspheres; wherein, the solid-liquid ratio of the thiolized composite porous microspheres to the oxidant was 1 g: 10 ml, the oxidation temperature was 75 ℃, and the oxidation time was 7 h.

[0066] E2. Preparation of raw material mixture Under stirring conditions of 20 rpm, the acidified composite porous microspheres were added to the suspension in portions; each addition of the acidified composite porous microspheres was 5% of the total amount.

[0067] E3. Isothermal reaction E3-1. Under stirring at 150 rpm, the raw material mixture is heated to 220℃ at a heating rate of 30℃ / min, and then subjected to the first esterification and held at that temperature for 4 hours.

[0068] E3-2. Under stirring at 50 rpm, the raw material mixture is heated from 220°C to 240°C at a heating rate of 3°C / min, and then subjected to the first polycondensation and heat preservation for 2 hours.

[0069] E3-3. Under stirring at 150 rpm, the raw material mixture was heated from 240°C to 255°C at a heating rate of 8°C / min, and then subjected to a second esterification and held at that temperature for 4 hours.

[0070] E3-4. Under stirring at 60 rpm, the raw material mixture is heated from 255℃ to 270℃ at a heating rate of 5℃ / min, and then subjected to a second polycondensation and held at that temperature for 2 hours.

[0071] E4. The product obtained from the isothermal reaction is melt-extruded at 250°C to obtain the flame-retardant engineering plastic of this embodiment.

[0072] Example 2 Example 2 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: 200 parts terephthalic acid, 120 parts ethylene glycol, 180 parts butylene glycol, 30 parts composite porous microspheres, 180 parts magnesium hydroxide microcapsules, 6 parts PET resin, and 5 parts PBT resin.

[0073] This embodiment also provides a method for preparing flame-retardant engineering plastics, with the same steps as in Embodiment 1.

[0074] Example 3 Example 3 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: 200 parts terephthalic acid, 150 parts ethylene glycol, 200 parts butylene glycol, 50 parts composite porous microspheres, 200 parts magnesium hydroxide microcapsules, 8 parts PET resin, and 8 parts PBT resin.

[0075] This embodiment also provides a method for preparing flame-retardant engineering plastics, with the same steps as in Embodiment 1.

[0076] Example 4 Example 4 provides a flame-retardant engineering plastic with the same raw material composition as Example 3.

[0077] This embodiment also provides a method for preparing flame-retardant engineering plastics, the steps of which are basically the same as those in Embodiment 3, except that: The isothermal reaction steps in step E3 are as follows: E3-1. Under stirring at 100 rpm, the raw material mixture is heated to 230℃ at a heating rate of 20℃ / min, and then subjected to the first esterification and held at that temperature for 3 hours.

[0078] E3-2. Under stirring at 60 rpm, the raw material mixture is heated from 230°C to 250°C at a heating rate of 5°C / min, and then subjected to the first polycondensation and held at that temperature for 1 hour.

[0079] E3-3. Under stirring at 200 rpm, the raw material mixture was heated from 250°C to 260°C at a heating rate of 10°C / min, and then subjected to a second esterification and held at that temperature for 3 hours.

[0080] E3-4. Under stirring at 50 rpm, the raw material mixture is heated from 260℃ to 290℃ at a heating rate of 3℃ / min, and then subjected to a second polycondensation and held at that temperature for 1 hour.

[0081] The melt extrusion temperature in step E4 is 260°C.

[0082] Example 5 Example 5 provides a flame-retardant engineering plastic with the same raw material composition as Example 3.

[0083] This embodiment also provides a method for preparing flame-retardant engineering plastics, the steps of which are basically the same as those in Embodiment 3, except that: The isothermal reaction steps in step E3 are as follows: E3-1. Under stirring at 200 rpm, the raw material mixture is heated to 230℃ at a heating rate of 40℃ / min, and then subjected to the first esterification and held at that temperature for 4 hours.

[0084] E3-2. Under stirring at 70 rpm, the raw material mixture is heated from 230°C to 250°C at a heating rate of 4°C / min, and then subjected to the first polycondensation and heat preservation for 2 hours.

[0085] E3-3. Under stirring at 100 rpm, the raw material mixture was heated from 250°C to 260°C at a heating rate of 9°C / min, and then subjected to a second esterification and held at that temperature for 4 hours.

[0086] E3-4. Under stirring at 70 rpm, the raw material mixture is heated from 260℃ to 280℃ at a heating rate of 4℃ / min, and then subjected to a second polycondensation and held at that temperature for 2 hours.

[0087] The melt extrusion temperature in step E4 is 260°C.

[0088] Comparative Example 1 Comparative Example 1 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: The mixture contains 200 parts terephthalic acid, 150 parts ethylene glycol, 200 parts butanediol, 50 parts composite porous microspheres, 200 parts magnesium hydroxide, 8 parts PET resin, and 8 parts PBT resin; wherein the average particle size of magnesium hydroxide is 30 μm.

[0089] This comparative example also provides a method for preparing flame-retardant engineering plastics, with steps that are basically the same as in Example 3.

[0090] Comparative Example 2 Comparative Example 2 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: 200 parts terephthalic acid, 150 parts ethylene glycol, 200 parts butylene glycol, 200 parts magnesium hydroxide microcapsules, 8 parts PET resin, and 8 parts PBT resin.

[0091] This comparative example also provides a method for preparing flame-retardant engineering plastics, with steps that are basically the same as in Example 3.

[0092] Comparative Example 3 Comparative Example 3 provides a flame-retardant engineering plastic, composed of the following parts by weight of raw materials: 100 parts PET resin, 100 parts PBT resin, 50 parts composite porous microspheres, and 200 parts magnesium hydroxide microcapsules.

[0093] This comparative example also provides a method for preparing flame-retardant engineering plastics, the steps of which are as follows: D1. At a rotation speed of 200 rpm, PET resin, PBT resin, composite porous microspheres and magnesium hydroxide microcapsules are mixed to obtain a mixture.

[0094] D2. The mixture is melt-extruded at 250°C.

[0095] To verify the advancement of the flame-retardant engineering plastic and its preparation method provided in the embodiments of the present invention, flame-retardant engineering plastics prepared by the preparation methods provided in the embodiments and comparative examples of the present invention were tested for flame retardancy and tensile strength. The results are shown in Table 1 below.

[0096] Table 1

[0097] From the table above, at least the following conclusions can be drawn: (1) For the data of Examples 1 to 3, when the same preparation conditions are used, the higher the content of magnesium hydroxide microcapsules in the raw materials, the higher the limiting oxygen index and elongation at break (tensile strength) of the flame-retardant engineering plastics prepared. It can be seen that in the flame-retardant engineering plastics provided by the embodiments of the present invention, magnesium hydroxide microcapsules can significantly improve the flame-retardant properties and tensile properties of the flame-retardant engineering plastics.

[0098] (2) For the data of Examples 3 to 5, when the raw material components are the same, different esterification and polycondensation reaction conditions have a certain impact on the limiting oxygen index of the prepared flame-retardant engineering plastics, but have little impact on the tensile properties. It can be seen that in the preparation method of flame-retardant engineering plastics provided by the embodiments of the present invention, the rotation speed and temperature of the esterification reaction and polycondensation reaction affect the dispersion uniformity of each component in the raw materials, thereby affecting the final flame-retardant properties and tensile properties of the product.

[0099] (3) Regarding the data from Example 3 and Comparative Example 1, the limiting oxygen index and elongation at break of the flame-retardant engineering plastic prepared using magnesium hydroxide microcapsules are significantly higher than those prepared directly using magnesium hydroxide. This indicates that the magnesium hydroxide microcapsules used in the flame-retardant engineering plastic provided in this embodiment of the invention have higher compatibility with other raw materials, thereby improving the dispersibility of magnesium hydroxide in the system and ultimately increasing the limiting oxygen index of the flame-retardant engineering plastic. Furthermore, polycarbonate has good flexibility, and when incorporated into the system as a shell material, it significantly improves the tensile properties of the flame-retardant engineering plastic.

[0100] (4) Regarding the data from Example 3 and Comparative Example 2, the limiting oxygen index of the flame-retardant engineering plastic prepared in Comparative Example 2 is much lower than that in Example 3. This is because the composite porous microspheres are made of alumina-modified silica, which can improve the flame-retardant performance of the flame-retardant engineering plastic (i.e., improve the limiting oxygen index). The elongation at break of the flame-retardant engineering plastic prepared in Comparative Example 2 is also much lower than that in Example 3. This is because the composite porous microspheres used in Example 3, after acidification treatment, can catalyze the esterification reaction of terephthalic acid, ethylene glycol, and butanediol with sulfonic acid groups. However, in Comparative Example 2, since acidified composite porous microspheres were not used, the esterification reaction of terephthalic acid, ethylene glycol, and butanediol was affected, thus affecting the tensile properties of the flame-retardant engineering plastic. Therefore, it can be seen that the use of composite porous microspheres in the raw materials of the flame-retardant engineering plastics provided in the embodiments of the present invention can significantly improve the limiting oxygen index and elongation at break of the flame-retardant engineering plastics.

[0101] (5) Regarding the data from Example 3 and Comparative Example 3, Comparative Example 3 directly mixed PET resin and PBT resin, and although the elongation at break of the flame-retardant engineering plastic prepared was relatively high, its limiting oxygen index was significantly reduced. Therefore, it can be seen that the method for preparing flame-retardant engineering plastics provided in this invention, by in-situ polymerizing terephthalic acid, ethylene glycol, and butanediol and intercalating them into the pores of the composite porous microspheres, can significantly improve the flame-retardant properties of the flame-retardant engineering plastics.

[0102] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A flame-retardant engineering plastic, characterized in that, The raw materials include the following parts by weight: 200 parts terephthalic acid, 100-150 parts ethylene glycol, 160-200 parts butylene glycol, 30-50 parts composite porous microspheres, 150-200 parts magnesium hydroxide microcapsules, 5-8 parts PET resin, and 5-8 parts PBT resin.

2. The flame-retardant engineering plastic according to claim 1, characterized in that, The average particle size of the terephthalic acid is 10 μm to 20 μm; And / or, the composite porous microspheres are alumina-modified silica porous microspheres; And / or, in the magnesium hydroxide microcapsules, the core material is nano-magnesium hydroxide and the shell material is polycarbonate; And / or, the average particle size of the magnesium hydroxide microcapsules is 20 μm to 40 μm; And / or, the average particle size of the PET resin is 10 μm to 30 μm; And / or, the average particle size of the PBT resin is 10 μm to 30 μm.

3. The flame-retardant engineering plastic according to claim 2, characterized in that, In the alumina-modified silica porous microspheres, the silicon-aluminum molar ratio is 50~70:

1.

4. A method for preparing a flame-retardant engineering plastic, characterized in that, Includes the following steps: The raw material mixture is melt-extruded after being reacted at a constant temperature. The raw material mixture contains terephthalic acid, ethylene glycol, butanediol, composite porous microspheres, magnesium hydroxide microcapsules, PET resin, and PBT resin.

5. The method for preparing flame-retardant engineering plastics according to claim 4, characterized in that, The preparation of the raw material mixture includes the following steps: The composite porous microspheres were acidified and then mixed with the suspension. The suspension contains terephthalic acid, ethylene glycol, butanediol, magnesium hydroxide microcapsules, PET resin, and PBT resin.

6. The method for preparing flame-retardant engineering plastics according to claim 5, characterized in that, The acidification process includes: The composite porous microspheres and 3-mercaptopropyltrimethoxysilane were mixed and refluxed in anhydrous toluene to obtain thiolized composite porous microspheres. The thiol-modified composite porous microspheres are oxidized with an oxidizing agent to obtain acidified composite porous microspheres.

7. The method for preparing flame-retardant engineering plastics according to claim 6, characterized in that, The solid-liquid ratio of the composite porous microspheres and 3-mercaptopropyltrimethoxysilane is 1g:10ml~20ml; And / or, the reflux reaction temperature is 110°C to 120°C; And / or, the reflux reaction time is 8h~10h; And / or, the oxidizing agent includes at least one of hydrogen peroxide and dilute nitric acid; And / or, the solid-liquid ratio of the thiolized composite porous microspheres to the oxidant is 1g:10ml~20ml.

8. The method for preparing flame-retardant engineering plastics according to any one of claims 4 to 7, characterized in that, The isothermal reaction step includes: The raw material mixture undergoes a first esterification stage, a first polycondensation stage, a second esterification stage, and a second polycondensation stage in sequence.

9. The method for preparing flame-retardant engineering plastics according to claim 8, characterized in that, The first esterification stage includes: heating the raw material mixture to 220°C to 230°C at a heating rate of 20°C / min to 40°C / min under stirring conditions of 100 rpm to 200 rpm, and then performing the first esterification and holding the temperature. And / or, the first polycondensation stage includes: heating the raw material mixture from 220°C to 230°C to 240°C to 250°C at a heating rate of 3°C / min to 5°C / min under stirring conditions of 50 rpm to 70 rpm, and then performing the first polycondensation heat preservation. And / or, the second esterification stage includes: heating the raw material mixture from 240°C to 250°C to 255°C to 260°C at a heating rate of 8°C / min to 10°C / min under stirring conditions of 100 rpm to 200 rpm, and then performing a second esterification and holding the temperature. And / or, the second polycondensation stage includes: heating the raw material mixture from 255°C to 260°C to 270°C to 290°C at a heating rate of 3°C / min to 5°C / min under stirring conditions of 50 rpm to 70 rpm, and then performing the second polycondensation and heat preservation. And / or, the temperature of the melt extrusion is 250°C to 260°C.

10. The application of a flame-retardant engineering plastic as described in any one of claims 1 to 3 in the field of pipes.

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