Flame-retardant drip-resistant polyester material and method for producing the same

Abstract

The application relates to the field of flame-retardant materials, and particularly discloses a flame-retardant and anti-dripping polyester material and a preparation method thereof. The preparation method of the polyester material comprises an esterification reaction and a polycondensation reaction. The copolymerization unit is introduced in the esterification stage to design the polyester molecular structure, promote the formation of carbon in the heating process, enhance the carbon residue, reduce the release of volatile products, and inhibit the melting and dripping phenomenon, so that the high-performance polyester material with excellent flame-retardant and anti-dripping and mechanical properties is obtained, and the defects of poor compatibility with a polymer matrix, unsatisfactory flame-retardant durability and mechanical property loss of an added flame retardant are solved.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials, specifically relating to a flame retardant and anti-drip polyester material and its preparation method. Background Technology

[0002] Polyester materials are widely used in packaging, construction, and home appliances. Their decomposition temperature is generally 420–450 °C, and the ignition point of their volatile components is mostly around 480 °C, making them flammable. When ignition occurs, polyester releases heat very quickly, with the time from ignition to maximum heat release being less than 15 seconds. Currently, with increased safety awareness and the development of product functionalization and differentiation, the flame retardancy and fire resistance of polyester materials have received widespread attention. Adding flame retardants is currently the main technical solution to improve the flame retardancy of materials. However, high-efficiency flame retardants, especially halogenated flame retardants such as decabromodiphenyl ether and decabromodiphenyl ether, decompose upon heating, producing toxic gases that pose a significant threat to human health and the environment. Furthermore, the extensive use of flame retardants can also affect the mechanical properties of materials. For example, phosphorus-containing flame retardants such as triphenyl phosphate and melamine can have different effects. The former can plasticize polyester to some extent, reducing its temperature tolerance; the latter can reduce the toughness of polyester to some extent, making the material brittle. Meanwhile, most phosphorus-containing copolyesters will drip during a fire, causing secondary injuries and burns to the human body. The high-temperature melt generated by the burning polymer dripping can ignite other objects, which is also one of the main reasons for the spread of fire.

[0003] To address the dripping phenomenon during polyurethane combustion, patent application CN102888012A discloses a method for preparing anti-drip flame-retardant polyester through radiation crosslinking. In this method, polyester chips are mixed with a radiation sensitizer and a flame retardant, extruded and granulated, and then processed into profiles. The resulting profiles are crosslinked by electron beam or gamma-ray radiation, thereby producing an anti-drip flame-retardant polyester that combines flame-retardant properties with anti-dripping effects. Patent application CN102534855B discloses a method for preparing durable halogen-free flame-retardant and anti-dripping polyester fibers. Nascent durable flame-retardant polyester fibers are irradiated in a high-energy electron accelerator (1.5–10 MeV) with an irradiation dose of 60–200 kGy to obtain durable halogen-free flame-retardant and anti-dripping polyester fibers that do not melt and drip during combustion, effectively preventing dripping and not releasing toxic hydrogen halide gas or fumes. Patent application CN101580976B discloses a method for preparing anti-drip flame-retardant polyester fiber, which involves mixing an anti-drip agent with polyester chips and then melt-spinning the mixture, followed by treatment with an alkaline solution, an acidic solution, and a post-treatment to obtain the anti-drip flame-retardant polyester fiber.

[0004] As can be seen from the aforementioned patent applications, the mainstream methods for mitigating dripping during material combustion are the addition of crosslinking agents and anti-dripping agents. Crosslinking is an effective method to promote char formation; during combustion, increased char formation on the surface of the material effectively prevents molten material from dripping. Currently, polytetrafluoroethylene (PTFE) is a widely used anti-dripping agent, which prevents dripping by increasing melt strength during combustion. However, these additives are prone to agglomeration and have poor dispersibility during use; furthermore, these additives can also have a certain degree of impact on the mechanical properties of the material. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention designs the molecular structure by introducing copolymer units during the esterification stage, which promotes char formation during heating, thereby enhancing char residue, reducing the release of volatile products, and suppressing dripping. This results in a high-performance polyester material that combines flame retardancy, anti-dripping properties, and excellent mechanical properties, solving the problems of poor compatibility with polymer matrix, unsatisfactory flame retardancy, and loss of mechanical properties associated with additive flame retardants.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing a flame-retardant and anti-drip polyester material, specifically comprising the following steps:

[0008] S1. Esterification reaction: The diacid is mixed with the modified monomer to obtain a mixed acid; the diol is mixed with the modified monomer to obtain a mixed alcohol; the mixed acid, mixed alcohol and esterification catalyst are stirred at 200-220℃ under 0.1-0.3 MPa or atmospheric pressure. When the amount of water removed reaches more than 80% of the theoretical value, the temperature is raised to 230-260℃ and stirring is continued. Stirring is stopped when the amount of water removed reaches 95% of the theoretical value.

[0009] S2. Polycondensation reaction: Depressurize to atmospheric pressure, add a polycondensation catalyst, control the reaction temperature at 270-285 ℃, reduce the pressure to 10-100 Pa, extract the by-products small molecule diols and oligomers, and when no by-products are extracted, purge with nitrogen to restore to atmospheric pressure to obtain a polymer melt. Cut the polymer melt into pellets to obtain a flame-retardant and anti-dripping polyester material.

[0010] The polyester material provided by this invention undergoes a rearrangement reaction during combustion to form a phenanthrene ring structure or a conjugated benzene ring structure, which is beneficial to the formation of carbon during combustion. A dense and stable carbon layer structure is formed on the surface of the polyester material, which prevents heat transfer and isolates oxygen, thus preventing the material from continuing to burn. At the same time, during the heating process, the relatively rigid aromatic structure gives the material a relatively high activation energy and good thermal stability under dynamic heating conditions.

[0011] In some embodiments, in step S1, the dicarboxylic acid is at least one selected from adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid, and sodium terephthalate.

[0012] Preferably, the dicarboxylic acid comprises terephthalic acid and sodium terephthalate.

[0013] On the one hand, this invention uses terephthalic acid as the main acid and introduces a modified monomer containing a double benzene ring to form a mixed acid system. The rigid aromatic ring structure of the modified monomer can be rearranged at high temperature to form a conjugated aromatic structure, which enhances the thermal stability of the carbon layer and significantly improves the heat resistance of the material. On the other hand, the sodium ions introduced by sodium terephthalate can form a physical cross-linking network through ionic bonds during combustion, which increases the melt viscosity and suppresses dripping.

[0014] In some embodiments, in step S1, the diol is at least one of butanediol, ethylene glycol, propylene glycol, 1,4-cyclohexanediol, diethylene glycol, and neopentyl glycol.

[0015] Preferably, the dicarboxylic acid comprises ethylene glycol and neopentyl glycol.

[0016] This invention uses a mixture of ethylene glycol and neopentyl glycol. Ethylene glycol has high reactivity, while the quaternary structure of neopentyl glycol gives it high stability and can reduce esterification side reactions. At the same time, the addition of neopentyl glycol can solve the hygroscopic effect caused by the introduction of sodium ions and improve the stability of the material.

[0017] In some embodiments, in step S1, the modified monomer comprises at least one of bisphenol A, bisphenol F, dihydroxybiphenyl, diphenyl ether dicarboxylic acid, and biphenyl dicarboxylic acid.

[0018] In some embodiments, in step S1, the average molar ratio of the mixed acid to the mixed alcohol is 1:(1.2 to 1.7).

[0019] In some embodiments, in step S1, the molar percentage of the modified monomer in the mixed acid is 0-10%.

[0020] In some embodiments, in step S1, the mixed alcohol contains 85-95% diol and 5-15% modified monomer, based on a molar percentage of 100%.

[0021] Preferably, the diol contains 50-80% ethylene glycol and 10-40% neopentyl glycol in molar proportion.

[0022] In some embodiments, in step S1, the esterification catalyst is a complex of zinc compound, manganese compound, and tin compound.

[0023] Preferably, the zinc compound comprises at least one of zinc oxide, zinc chloride, zinc acetate, and zinc octanoate; the manganese compound comprises at least one of manganese oxide, manganese acetate, and manganese carbonate; and the tin compound comprises at least one of tin oxide, stannous chloride, stannous octanoate, dibutyltin diacetate, and tetrabutyltin.

[0024] This invention improves reaction efficiency through the synergistic effect of zinc, manganese, and tin composite catalysts, mainly by forming complexes with carboxylic acids, promoting proton transfer and carboxylic acid activation, and reducing the reaction activation energy.

[0025] Furthermore, the mass ratio of zinc compound, manganese compound, and tin compound in the esterification catalyst is (1-1.25):(1-5):(0.5-2).

[0026] In some embodiments, in step S2, the polycondensation catalyst is a complex of antimony compound, titanium compound, and germanium compound.

[0027] Preferably, the antimony compound comprises at least one of antimony trioxide, antimony pentoxide, antimony acetate, and antimony glycol; the titanium compound comprises at least one of tetrabutyl titanate, tetraisopropyl titanate, and ethylene glycol titanate; and the germanium compound comprises at least one of germanium dioxide, germanium tetrachloride, germanium acetate, and germanium glycol.

[0028] In the composite catalyst system of antimony, titanium, and germanium compounds, the antimony catalyst promotes the coupling of molecular chain end groups through the coordination of hydroxyl oxygen. The titanium-germanium composite system reduces the side reactions caused by the high activity of titanium catalysts and improves thermal stability, alleviating the melt yellowing caused by the easy thermal degradation of titanium catalysts. At the same time, the antimony compound compensates for the hydrolysis sensitivity of titanium catalysts.

[0029] Furthermore, the mass ratio of antimony compound, titanium compound, and germanium compound in the polycondensation catalyst is (1-5):(0.2-0.8):(0.1-0.5).

[0030] In another aspect, the present invention provides a flame-retardant and anti-drip polyester material prepared by the above-mentioned technical solution, wherein the limiting oxygen index of the flame-retardant and anti-drip polyester material is >30%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention provides a method for producing flame-retardant, non-dripping polyester free of nitrogen, phosphorus, and halogen flame-retardant elements, which improves the environmental friendliness of the production process. By introducing copolymer units during the esterification stage and designing their molecular structure, the method promotes char formation during the heating process, thereby enhancing char residue, reducing the release of volatile products, and suppressing dripping. The resulting polyester material is not limited to the single indicator of flame retardancy, but also has flame retardancy, anti-dripping properties, and mechanical properties. This solves the shortcomings of additive flame retardants, such as poor compatibility with the polymer matrix, unsatisfactory flame retardant durability, and loss of mechanical properties.

[0033] 2. In this invention, terephthalic acid and modified monomers containing diphenyl rings can be rearranged at high temperature to form a conjugated aromatic structure, thereby enhancing the thermal stability of the carbon layer and significantly improving the heat resistance of the material; at the same time, sodium ions introduced by sodium terephthalate can form a physical cross-linking network through ionic bonds during combustion, thereby increasing the melt viscosity and suppressing droplets.

[0034] 3. This invention uses a mixture of ethylene glycol and neopentyl glycol. Ethylene glycol has high reactivity, while the quaternary structure of neopentyl glycol gives it high stability, which can reduce esterification side reactions. At the same time, the addition of neopentyl glycol can solve the hygroscopic effect caused by the introduction of sodium ions and improve the stability of the material.

[0035] 4. In the polycondensation reaction, the present invention adopts an antimony, titanium and germanium composite catalytic system. The antimony catalyst promotes the coupling of molecular chain end groups by coordinating hydroxyl oxygen. The titanium-germanium composite system can reduce the side reactions caused by the high activity of titanium catalysts, while improving thermal stability and alleviating the melt yellowing caused by the easy thermal degradation of titanium catalysts. At the same time, the antimony compound compensates for the hydrolysis sensitivity of titanium catalysts. Detailed Implementation

[0036] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0037] It is worth noting that, unless otherwise specified, the raw materials used in the following preparation examples and embodiments are all from any commercially available manufacturer.

[0038] Example 1

[0039] A method for preparing a flame-retardant and anti-drip polyester material specifically includes the following steps:

[0040] S1. Esterification reaction: 6 mol of terephthalic acid, 0.1 mol of sodium terephthalate, and 0.3 mol of biphenyl acid are mixed to obtain a mixed acid; 5.4 mol of ethylene glycol, 2.7 mol of neopentyl glycol, and 0.9 mol of bisphenol F are mixed to obtain a mixed alcohol; the mixed acid, mixed alcohol, 0.3387 g of zinc acetate, 1.1338 g of manganese acetate, and 0.0958 g of stannous chloride are stirred at 210°C under 0.2 MPa conditions. When the amount of dehydrated water reaches more than 80% of the theoretical value, the temperature is raised to 250°C and stirring continues until the amount of dehydrated water reaches 95% of the theoretical value, at which point stirring is stopped.

[0041] S2. Polycondensation reaction: Depressurize to atmospheric pressure, add 0.5010 g antimony glycol, 0.2560 g tetrabutyl titanate, and 0.0173 g germanium dioxide. Control the reaction temperature at 280℃, reduce the pressure to 60 Pa, and remove the by-products small molecule diols and oligomers. When no by-products are removed, purge with nitrogen to restore atmospheric pressure, and obtain a polymer melt. Cut the polymer melt into pellets to obtain a flame-retardant and anti-drip polyester material.

[0042] Example 2

[0043] A method for preparing a flame-retardant and anti-drip polyester material specifically includes the following steps:

[0044] S1. Esterification reaction: 6 mol of terephthalic acid, 0.1 mol of sodium terephthalate, and 0.3 mol of diphenyl ether dicarboxylic acid are mixed to obtain a mixed acid; 4 mol of ethylene glycol, 2.8 mol of neopentyl glycol, and 1.2 mol of dihydroxybiphenyl are mixed to obtain a mixed alcohol; the mixed acid, mixed alcohol, 0.3387 g of zinc acetate, 1.1338 g of manganese acetate, and 0.0958 g of stannous chloride are stirred at 220°C under normal pressure. When the amount of water removed reaches more than 80% of the theoretical value, the temperature is raised to 260°C and stirring continues until the amount of water removed reaches 95% of the theoretical value, at which point stirring is stopped.

[0045] S2. Polycondensation reaction: Depressurize to atmospheric pressure, add 0.5010 g antimony glycol, 0.2560 g tetrabutyl titanate, and 0.0173 g germanium dioxide. Control the reaction temperature at 270℃, reduce the pressure to 30 Pa, and remove the by-products small molecule diols and oligomers. When no by-products are removed, purge with nitrogen to restore atmospheric pressure, and obtain a polymer melt. Cut the polymer melt into pellets to obtain a flame-retardant and anti-drip polyester material.

[0046] Example 3

[0047] A method for preparing a flame-retardant and anti-drip polyester material specifically includes the following steps:

[0048] S1. Esterification reaction: 6 mol of terephthalic acid, 0.1 mol of sodium terephthalate, and 0.5 mol of biphenyl acid are mixed to obtain a mixed acid; 8.8 mol of ethylene glycol, 1.65 mol of neopentyl glycol, and 0.55 mol of bisphenol A are mixed to obtain a mixed alcohol; the mixed acid, mixed alcohol, 0.3387 g of zinc acetate, 1.1338 g of manganese acetate, and 0.0958 g of stannous chloride are stirred at 200°C under 0.3 MPa. When the amount of water removed reaches more than 80% of the theoretical value, the temperature is raised to 230°C and stirring is continued until the amount of water removed reaches 95% of the theoretical value, at which point stirring is stopped.

[0049] S2. Polycondensation reaction: Depressurize to atmospheric pressure, add 0.5010 g antimony glycol, 0.2560 g tetrabutyl titanate, and 0.0173 g germanium dioxide. Control the reaction temperature at 280℃, reduce the pressure to 80 Pa, and remove the by-products small molecule diols and oligomers. When no by-products are removed, purge with nitrogen to restore atmospheric pressure, and obtain a polymer melt. Cut the polymer melt into pellets to obtain a flame-retardant and anti-drip polyester material.

[0050] Example 4

[0051] This embodiment provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as that in Embodiment 1, except that in step S1, sodium terephthalate is replaced by an equal amount of terephthalic acid.

[0052] Example 5

[0053] This embodiment provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as that in Embodiment 1, except that in step S1, neopentyl glycol is replaced by an equal amount of ethylene glycol.

[0054] Example 6

[0055] This embodiment provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as that in Embodiment 1, except that in step S2, antimony glycolate is replaced by an equal amount of tetrabutyl titanate.

[0056] Example 7

[0057] This embodiment provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as in Embodiment 1, except that step S1 is replaced with:

[0058] S1. Esterification reaction: Mix 6 mol of terephthalic acid, 0.1 mol of sodium terephthalate and 0.3 mol of biphenyl acid to obtain a mixed acid; mix the mixed acid, 5.9 mol of ethylene glycol, 3.1 mol of neopentyl glycol, 0.3387 g of zinc acetate, 1.1338 g of manganese acetate and 0.0958 g of stannous chloride at 0.2 MPa and 210 °C. When the amount of water removed reaches more than 80% of the theoretical value, raise the temperature to 250 °C and continue stirring. Stop stirring when the amount of water removed reaches 95% of the theoretical value.

[0059] Example 8

[0060] This embodiment provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as in Embodiment 1, except that step S1 is replaced with:

[0061] S1. Esterification reaction: Mix 5.4 mol ethylene glycol, 2.7 mol neopentyl glycol, and 0.9 mol bisphenol F to obtain a mixed alcohol; mix 6.2 mol terephthalic acid, 0.2 mol sodium terephthalate, the mixed alcohol, 0.3387 g zinc acetate, 1.1338 g manganese acetate, and 0.0958 g stannous chloride at 0.2 MPa and 210 °C. When the amount of water removed reaches more than 80% of the theoretical value, raise the temperature to 250 °C and continue stirring until the amount of water removed reaches 95% of the theoretical value, then stop stirring.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a flame-retardant and anti-drip polyester material. The specific implementation method is the same as in Example 1, except that step S1 is replaced with:

[0064] S1. Esterification reaction: Mix 6 mol terephthalic acid, 0.1 mol sodium terephthalate, 5.4 mol ethylene glycol, and 2.7 mol neopentyl glycol, then add 0.3387 g zinc acetate, 1.1338 g manganese acetate, and 0.0958 g stannous chloride. Stir at 210°C under 0.2 MPa conditions. When the amount of dehydrated water reaches more than 80% of the theoretical value, raise the temperature to 250°C and continue stirring. Stop stirring when the amount of dehydrated water reaches 95% of the theoretical value.

[0065] Performance testing:

[0066] Thermal decomposition of 5% (T) was obtained through TGA testing. 5% Temperature, residual amount at 800 ℃, and limiting oxygen index (LOI); UL-94 index is obtained using a flammability tester, with flammability levels from low to high being V-0, V-1, V-2, and V-3; impact strength test standard is GB / T 1843-2008.

[0067] The results are shown in Table 1.

[0068] Table 1

[0069]

[0070] In Table 1, different dicarboxyl and dihydroxy modified monomers were added to the diacid and diol in Examples 1-3. TGA test results showed that the thermal decomposition of the polyester materials obtained from the three methods was 5% (T... 5% The residual rate reached 32% at temperatures above 430°C and 800°C, and the limiting oxygen index was greater than 30%. The flame retardant rating reached V-0, and no dripping phenomenon was observed during the test.

[0071] Compared to Example 1, Examples 7 and 8 introduced modified monomers into the diacid and diol separately, respectively, which reduced the benzene ring content and thus decreased the flame retardant effect. Furthermore, in Comparative Example 1, the diacid and diol were reacted directly. The data showed that the char residue rate of the polyester material at 800°C was significantly lower without the addition of modified monomers. This may be because the lack of benzene ring rearrangement reaction to form phenanthrene ring structure or conjugated benzene ring structure during combustion is not conducive to char formation.

[0072] Compared to Example 1, Example 4 did not add sodium terephthalate. Although no dripping phenomenon was observed during the test, the char residue rate decreased. This may be because the sodium ions introduced by sodium terephthalate can form a physical cross-linking network through ionic bonds during combustion, which increases the melt viscosity, reduces the release of volatile products, and thus enhances the char residue.

[0073] Compared to Example 1, in Example 5, neopentyl glycol was replaced with ethylene glycol in the diol, which is detrimental to reaction stability and results in a certain decrease in polyester yield. The polycondensation reaction in Example 6 used a tetrabutyl titanate-germanium dioxide composite catalyst, which lacked the synergistic effect of antimony compounds, also affecting the yield, possibly due to the hydrolytic sensitivity of the titanium catalyst.

[0074] The embodiments and comparative examples described above do not limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a flame-retardant and anti-drip polyester material, characterized in that, Specifically, it includes the following steps: S1. Esterification reaction: The diacid is mixed with the modified monomer to obtain a mixed acid; the diol is mixed with the modified monomer to obtain a mixed alcohol; the mixed acid, mixed alcohol and esterification catalyst are stirred at 200-220℃ under 0.1-0.3 MPa or atmospheric pressure. When the amount of dewatered reaches more than 80% of the theoretical value, the temperature is raised to 230-260℃ and stirring is continued. Stirring is stopped when the amount of dewatered reaches 95% of the theoretical value. S2. Polycondensation reaction: Depressurize to normal pressure, add polycondensation catalyst, control the reaction temperature at 270-285 ℃, reduce pressure to 10-100 Pa, extract by-products small molecule diols and oligomers, and when no by-products are extracted, purge with nitrogen to restore to normal pressure to obtain polymer melt. Cut the polymer melt into pellets to obtain a viscosity-resistant flame-retardant and anti-dripping polyester material. The modified monomer contains at least one of bisphenol A, bisphenol F, dihydroxybiphenyl, diphenyl ether dicarboxylic acid, and biphenyl dicarboxylic acid; The dicarboxylic acid includes terephthalic acid and sodium terephthalate; The diol comprises ethylene glycol and neopentyl glycol; The polycondensation catalyst is a complex of antimony compounds, titanium compounds, and germanium compounds.

2. The method for preparing the flame-retardant and anti-drip polyester material according to claim 1, characterized in that, In step S1, the average molar ratio of the mixed acid to the mixed alcohol is 1:(1.2 to 1.7).

3. The method for preparing the flame-retardant and anti-drip polyester material according to claim 1, characterized in that, In step S1, the molar percentage of the modified monomer in the mixed acid is 0-10%.

4. The method for preparing the flame-retardant and anti-drip polyester material according to claim 1, characterized in that, In step S1, based on a molar percentage of 100%, the mixed alcohol contains 85-95% diol and 5-15% modified monomer.

5. The method for preparing the flame-retardant and anti-drip polyester material according to claim 1, characterized in that, In step S1, the esterification catalyst is a complex of zinc compound, manganese compound, and tin compound.

6. A flame-retardant and anti-drip polyester material obtained by the preparation method according to any one of claims 1-5, characterized in that, The limiting oxygen index of the flame-retardant and drip-proof polyester material is >30%.

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