Preparation method of halogen-free antimony-free flame-retardant polyester

Abstract

The invention relates to the field of polyester, and discloses a halogen-free antimony-free flame-retardant polyester preparation method, which comprises: 1) grinding a magnesium compound catalytic promoter, and crushing under liquid nitrogen cooling; then dispersing a catalytic promoter in ethylene glycol to obtain a catalytic promoter dispersion liquid; 2) mixing and esterifying dibasic acid, dihydric alcohol and a flame retardant dihydric alcohol esterifying liquid; 3) after esterification is finished, adding a titanium catalyst and a catalytic promoter dispersion liquid; and carrying out preshrinking and final shrinkage reactions to obtain the halogen-free antimony-free flame-retardant polyester. According to the invention, a titanium catalyst is compounded with a magnesium compound to serve as a catalytic promoter, so that the problem of yellowing of polyester caused by the titanium catalyst can be solved on the premise of realizing antimony-free environmental protection; and meanwhile, the magnesium compound catalytic promoter can also form a magnesium oxide layer and water vapor when the polyester is combusted, so that heat transfer can be reduced, the oxygen concentration can be diluted, and molten drops generated when the polyester is combusted can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of polyester, and in particular to a method for preparing halogen-free and antimony-free flame-retardant polyester. Background Art

[0002] Polyethylene terephthalate (PET) has excellent mechanical properties, heat resistance, stability, and electrical insulation, and is widely used in aerospace, automotive, electrical and electronic, construction, and other industries. However, the limiting oxygen index of ordinary polyester is only 21, which means that it is extremely flammable in air. Once a fire occurs, the fire spreads rapidly. In addition, molten dripping will occur during the combustion process of polyester, which not only accelerates the spread of fire, but may also cause secondary fire damage, seriously limiting the application of polyester in places with high fire safety requirements.

[0003] In order to give polyester flame retardant properties, the research and development of flame retardant copolyesters has gradually become a hot topic. In the preparation process of flame retardant copolyesters, the commonly used catalysts are mostly antimony compounds. Although these antimony-containing catalysts can promote the reaction and improve the flame retardant effect to a certain extent, the antimony element poses potential environmental and health hazards. For example, patent CN105463610A discloses a method for preparing flame retardant polyester fibers using ethylene glycol antimony and ethylene glycol magnesium as catalysts and 2-carboxyethylphenyl hypophosphorous acid as a flame retardant. The flame retardant polyester prepared by this method has an oxygen index greater than 30 and exhibits good flame retardant properties. However, this method still uses an antimony-containing catalyst, and in the subsequent use process, the antimony element in the polyester is a potential harmful substance.

[0004] In recent years, titanium-based catalysts have garnered significant attention in the application of flame-retardant copolyesters. However, flame-retardant copolyester chips produced using titanium-based catalysts suffer from a significant yellowing problem. This phenomenon severely impacts the product's appearance and application, particularly in areas requiring high color, such as high-end textiles and electronic and electrical housings, limiting their further promotion and application.

[0005] Patent CN115852518A discloses a melt-spun process for producing antimony-free, matte-resistant, flame-retardant polyester fibers. This method uses nano-zinc oxide as a catalyst, overcoming, to some extent, the inherent drawbacks of the blending method for preparing flame-retardant polyesters, resulting in enhanced stability and more uniform dispersion of the flame-retardant component. However, from a catalytic performance perspective, metallic zinc has relatively low catalytic activity, requiring a much higher amount than titanium catalysts in the polymerization reaction, which in turn slows the polymerization rate and prolongs the reaction cycle. Furthermore, the presence of zinc exacerbates the thermal degradation of polyester, negatively impacting the quality of the polyester product and causing a significant decline in its quality. Summary of the Invention

[0006] The present invention aims to address existing polyester flame-retardant technologies by providing a halogen-free, antimony-free polyester material with excellent flame-retardant properties and a high oxygen index. This invention utilizes a titanium-based catalyst combined with a magnesium compound as a catalyst co-agent, addressing the yellowing problem of polyester caused by titanium-based catalysts while achieving an antimony-free and environmentally friendly process. Furthermore, the magnesium compound catalyst co-agent forms a magnesium oxide layer and water vapor during polyester combustion, thereby reducing heat transfer, diluting oxygen concentration, and reducing the generation of molten droplets during polyester combustion.

[0007] The specific technical solution of the present invention is: a method for preparing halogen-free and antimony-free flame-retardant polyester, which comprises the following steps: 1) The catalyst promoter is ground and then pulverized under liquid nitrogen cooling; then the magnesium compound is dispersed in ethylene glycol as the catalyst promoter to obtain a catalyst promoter dispersion.

[0008] 2) Mixing and esterifying the dibasic acid, diol and flame retardant diol esterification liquid.

[0009] 3) After the esterification is completed, a titanium catalyst and a catalyst promoter dispersion are added; and after pre-shrinkage and final shrinkage reactions, a halogen-free and antimony-free flame-retardant polyester is obtained.

[0010] The catalyst of the present invention uses a titanium-based catalyst, which is safer and more environmentally friendly than antimony-free catalysts. The present invention has found that by compounding a magnesium compound as a catalytic co-agent on this basis, the yellowing of slices caused by titanium-based catalysts can be effectively improved. Specifically: First, the magnesium compound catalytic co-agent can slow down the side reactions triggered by the titanium-based catalyst, reduce the oxidation reaction of the polyester during polycondensation, and reduce the generation of colored groups; second, the magnesium compound catalytic co-agent can reduce the thermal oxidative degradation caused by the titanium-based catalyst during the polycondensation process, reduce the degradation of the polyester molecular chain, and reduce the generation of unsaturated bonds and chromophores; finally, magnesium hydroxide, as a substance with abundant surface alkaline catalytic sites, can effectively react with acidic substances. This reaction belongs to the category of acid-base reactions for catalytic polycondensation. By compounding magnesium hydroxide with a titanium-based catalyst, its surface properties and electronic structure can be significantly improved, thereby improving its catalytic activity. This improvement helps to reduce undesirable reaction sites between the titanium-based catalyst and the flame retardant, thereby reducing the generation of colored groups. This method effectively reduces the number of colored groups, which is crucial for improving the color and stability of the material. The magnesium compound catalyst promoter reduces the interaction between the titanium catalyst and impurities in the raw material, reducing the production of colored substances. Furthermore, the magnesium compound catalyst promoter forms a magnesium oxide layer with water vapor during combustion, thereby reducing heat transfer, diluting oxygen concentration, and reducing the amount of molten droplets produced during polyester combustion.

[0011] In addition, the flame retardant diol esterification liquid used in the present invention can greatly reduce the steric hindrance between the flame retardant and the polyester compared to directly adding the flame retardant, thereby increasing the polymerization degree of the flame retardant and the matrix without affecting the subsequent processing performance.

[0012] Preferably, in step 1), the catalyst aid is one or more of magnesium oxide, magnesium chloride, magnesium hydroxide, magnesium carbonate, magnesium sulfate and magnesium bicarbonate; most preferably, magnesium hydroxide.

[0013] Selecting the above-mentioned magnesium compounds as catalyst co-agents (especially magnesium hydroxide) not only can alleviate the yellowing problem of polyester caused by titanium catalysts, but also can decompose magnesium hydroxide to produce magnesium oxide and water when the polyester burns. In this process, it absorbs a large amount of heat, thereby effectively reducing the surface temperature of the burning material, effectively slowing the decomposition rate of the polyester, and reducing the production of combustible gases and toxic and harmful substances. The water produced by decomposition, under the support of heat, will form a large amount of water vapor, which can occupy the space in the combustion area, making it difficult for oxygen to reach the surface of the burning material, and effectively suppressing the combustion reaction. The magnesium oxide produced by decomposition is a good refractory material that can adhere to the surface of the combustible material, forming a dense protective film that can prevent oxygen from contacting the combustible material, while also preventing heat transfer and the escape of combustible gases. The magnesium oxide on the polyester surface can promote the carbonization of the polyester surface, forming a carbonized layer that blocks heat and oxygen from entering the polymer interior, and also prevents heat transfer and the escape of combustible gases, further enhancing the flame retardant effect. Magnesium oxide can also neutralize acidic gases produced by polyester combustion, such as carbon dioxide and nitrogen oxides, reducing the toxic and harmful gases produced by polymer combustion.

[0014] In addition, the present invention has found that since the chemical properties of the magnesium compound are easily destroyed by high temperature during the pulverization process in the pulverizer, adding liquid nitrogen during the pulverization process can prevent the high temperature from destroying the chemical properties of the catalyst promoter.

[0015] Preferably, in step 1), the D90 of the catalyst promoter in the catalyst promoter dispersion is ≤≤1 μm.

[0016] Since fiber-grade slices are prepared, larger particle sizes will affect the spinning assembly and polymerization filter. During preparation, large-size particles are processed to less than 5 microns for use.

[0017] Preferably, in step 1), the mass ratio of the catalyst promoter to ethylene glycol is 1:(7-11).

[0018] Preferably, in step 2), the flame retardant in the flame retardant diol esterification liquid is one or both of 2-carboxyethylphenylphosphinate (CEPPA) or [(6-oxo-6H-dibenzo[1,2]oxaphosphorin-6-yl)methyl]succinic acid (DDP); more preferably 2-carboxyethylphenylphosphinate (CEPPA).

[0019] The present invention selects a phosphorus-based reactive flame retardant, which can participate in the polyester polymerization process, has little effect on the molecular regularity of the polyester itself, and does not affect the crystallization behavior and post-processing performance of the slices.

[0020] Preferably, in step 2), the diol in the flame retardant diol esterification liquid is one or more of ethylene glycol, propylene glycol, butanediol, pentanediol and 1,4-cyclohexanedimethanol.

[0021] Preferably, in step 2), the molar ratio of the dibasic acid to the diol is 1:(1.1-1.4).

[0022] Preferably, in step 2), the amount of the flame retardant diol esterification liquid is 0.5-0.8 wt % of the total amount of the polyester product.

[0023] Preferably, in step 2), the reaction temperature of the esterification is 180-250° C., and the reaction pressure is 0-0.40 MPa.

[0024] Preferably, in step 3), the titanium-based catalyst is one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraisooctyl titanate, methyl titanate, titanium isobutoxide and tetrabutyl titanate.

[0025] Preferably, in step 3), the catalyst accounts for 1-100 ppm of the total amount of the polyester product.

[0026] Preferably, in step 3), the catalyst auxiliary accounts for 500-6000 ppm of the total polyester product.

[0027] Theoretically, the more catalytic additives are added, the better the flame retardant effect will be. However, since magnesium compounds (such as magnesium hydroxide) themselves have a certain catalytic effect and cross-linking occurs, when the amount added is too much, the cross-linking is very serious and the total product obtained is very small, which does not meet production requirements. Excessive use will also cause more frequent pressure changes of components and filters; conversely, if the amount used is too little, the improvement effect will not be obvious.

[0028] Preferably, in step 3), the reaction temperature of the pre-shrinkage is 240-280°C and the pressure is 0.1-3 kPa; the reaction temperature of the final shrinkage is 270-285°C and the pressure is 30-200 Pa; Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a titanium-based catalyst combined with a magnesium compound as a catalytic co-agent, which can solve the yellowing problem of polyester caused by titanium-based catalysts while achieving antimony-free and environmentally friendly properties. After adding a specific magnesium compound catalytic co-agent, the various properties of titanium-based flame-retardant polyester chips show significant changes. In terms of color value, it has been extremely effectively improved, and the problems that may have existed, such as uneven color, yellowing or dullness, have been alleviated, making the titanium-based flame-retardant polyester chips more uniform and bright in appearance and color, meeting higher quality standards.

[0029] (2) The magnesium compound catalyst co-acting agent of the present invention can form a magnesium oxide layer and water vapor during polyester combustion, thereby reducing heat transfer and diluting oxygen concentration, resulting in a significant reduction in the number of molten droplets, a key indicator of flame retardancy. This means that when exposed to dangerous conditions such as high temperatures or fire, the titanium-based flame-retardant polyester can better maintain its morphological integrity, reducing the secondary hazards that may be caused by molten droplets, thereby greatly improving its flame retardant safety and reliability.

[0030] (3) Overall, due to the optimization of color value and the effective control of the number of molten droplets, the overall quality of the titanium-based flame-retardant polyester of the present invention has been substantially improved in many aspects. This has extremely important significance and value for the expansion of its application in related fields and the enhancement of product market competitiveness, and has laid a solid and good foundation for its subsequent large-scale production and wide application. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the embodiments.

[0032] Overall embodiment A method for preparing a halogen-free and antimony-free flame-retardant polyester comprises the following steps: 1) The catalyst promoter is ground and then pulverized under liquid nitrogen cooling; and then the catalyst promoter is dispersed in ethylene glycol to obtain a catalyst promoter dispersion.

[0033] In some preferred implementation cases, the catalyst promoter is one or more of magnesium oxide, magnesium chloride, magnesium hydroxide, magnesium carbonate, magnesium sulfate and magnesium bicarbonate.

[0034] In some preferred implementation cases, the catalyst aid is magnesium hydroxide.

[0035] In some preferred implementation cases, the D90 of the catalyst promoter in the catalyst promoter dispersion is ≤≤1 μm.

[0036] In some preferred implementation cases, the mass ratio of the catalyst promoter to ethylene glycol is 1:(7-11).

[0037] 2) Mixing and esterifying the dibasic acid, diol and flame retardant diol esterification liquid.

[0038] In some preferred implementation cases, the flame retardant in the flame retardant diol esterification liquid is one or both of 2-carboxyethylphenyl hypophosphite (CEPPA) or [(6-oxo-6H-dibenzo[1,2]oxaphosphorin-6-yl)methyl]succinic acid (DDP); more preferably 2-carboxyethylphenyl hypophosphite (CEPPA).

[0039] In some preferred implementation cases, the diol in the flame retardant diol esterification liquid is one or more of ethylene glycol, propylene glycol, butanediol, pentanediol and 1,4-cyclohexanedimethanol.

[0040] In some preferred embodiments, the molar ratio of the dibasic acid to the diol is 1:(1.1-1.4).

[0041] In some preferred implementation cases, the amount of the flame retardant diol esterification liquid accounts for 0.5-0.8 wt % of the total amount of the polyester product.

[0042] In some preferred implementation cases, the reaction temperature of the esterification is 180-250° C., and the reaction pressure is 0-0.40 MPa.

[0043] 3) After the esterification is completed, a titanium catalyst and a catalyst promoter dispersion are added; and after pre-shrinkage and final shrinkage reactions, a halogen-free and antimony-free flame-retardant polyester is obtained.

[0044] In some preferred implementation cases, the titanium-based catalyst is one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraisooctyl titanate, methyl titanate, titanium isobutoxide, and tetrabutyl titanate.

[0045] In some preferred embodiments, the catalyst accounts for 1-100 ppm of the total polyester product.

[0046] In some preferred embodiments, the catalyst auxiliary accounts for 500-6000 ppm of the total polyester product.

[0047] In some preferred implementation cases, the reaction temperature of the pre-shrinkage is 240-280° C. and the pressure is 0.1-3 kPa; the reaction temperature of the final shrinkage is 270-285° C. and the pressure is 30-200 Pa; Furthermore, the halogen-free and antimony-free flame-retardant polyester is prepared into a composite halogen-free and high-phosphorus content flame-retardant polyester injection molding strip, including the following steps: drying the halogen-free and antimony-free flame-retardant polyester slices under vacuum conditions of 80-120°C, and then injection molding after drying; and conducting an oxygen index test in accordance with the requirements of the national standard GB / T2406-2009.

[0048] Furthermore, the halogen-free and antimony-free flame-retardant polyester is prepared into a halogen-free and antimony-free flame-retardant polyester fiber, comprising the following steps: drying the halogen-free and antimony-free flame-retardant polyester according to the following conditions: under vacuum conditions, first heating to 65-75°C and drying for 1-3 hours, keeping warm at 65-75°C for 1-3 hours, then heating to 100-120°C and drying for 1-3 hours, and continuing to dry at 100-120°C for 8-10 hours. After drying, spinning is carried out to obtain a halogen-free and antimony-free flame-retardant polyester fiber.

[0049] Specific Examples and Comparative Examples Example 1: A composite halogen-free and antimony-free flame-retardant polyester chip, the preparation method of which comprises the following steps: (1) Preparation of catalyst promoter dispersion: A certain amount of catalyst promoter magnesium hydroxide was added to a mortar and ground in a clockwise direction for 10 minutes; the ground catalyst promoter was placed in a grinder and ground for 5 minutes. A certain amount of liquid nitrogen was added during the grinding to prevent high temperature from destroying the chemical properties of the catalyst promoter. After grinding to D90≤≤1 μm, it was mixed with ethylene glycol in a ratio of 1:9 and ground in a grinder to obtain a catalyst promoter dispersion.

[0050] (2) Add terephthalic acid, diol (alcohol-acid molar ratio 1:1.3), and flame retardant esterification liquid (phosphorus content is controlled at 6500 ppm of the final polyester product) into the reactor to carry out esterification reaction; the esterification temperature is controlled at 230℃-250℃, the esterification pressure is controlled at 0.4Mpa, and the esterification time is controlled at 3h.

[0051] (3) After the esterification is completed, tetrabutyl titanate and a catalyst dispersion liquid accounting for 7 ppm of the total polyester (the catalyst content is controlled to be 1000 ppm of the total polyester).

[0052] (4) After stirring evenly, perform low vacuum pre-shrinkage reaction, control the pre-shrinkage temperature at 250°C-280°C, slowly control the vacuum degree to 1.5kPa, and pre-shrinkage time is about 50 minutes to discharge excess diol.

[0053] (5) After the pre-shrinkage is completed, the high vacuum final shrinkage reaction is carried out, the polycondensation temperature is controlled at 270°C-285°C, the polycondensation vacuum is controlled at 200 Pa, and the polycondensation time is about 1.5 hours to obtain a product melt. The melt is then allowed to stand, discharged, and pelletized to obtain halogen-free and antimony-free flame-retardant polyester chips.

[0054] (6) Preparation of composite halogen-free and antimony-free flame-retardant polyester injection molding strips: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried under vacuum at 100° C. and injection molded; an oxygen index test is performed in accordance with the requirements of the national standard GB / T2406-2009.

[0055] (7) Preparation of halogen-free and antimony-free flame-retardant polyester fiber: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried according to the following conditions: first, under vacuum conditions, the temperature is raised to 70°C and dried for 2 hours, then kept at 70°C for 2 hours, then the temperature is raised to 110°C and dried for 2 hours, and the drying is continued at 110°C for 9 hours. After the drying is completed, the halogen-free and antimony-free flame-retardant polyester fiber is spun.

[0056] Example 2: A composite halogen-free and antimony-free flame-retardant polyester chip, the preparation method of which comprises the following steps: (1) Preparation of catalyst promoter dispersion: A certain amount of catalyst promoter magnesium hydroxide was added to a mortar and ground in a clockwise direction for 10 minutes; the ground catalyst promoter was placed in a grinder and ground for 5 minutes. A certain amount of liquid nitrogen was added during the grinding to prevent high temperature from destroying the chemical properties of the catalyst promoter. After grinding to D90≤≤1 μm, it was mixed with ethylene glycol in a ratio of 1:9 and ground in a grinder to obtain a catalyst promoter dispersion.

[0057] (2) Adding terephthalic acid, diol (alcohol-acid molar ratio of 1:1.3), and flame retardant esterification liquid (phosphorus content is controlled at 6500 ppm of the final polyester product) into the reactor to carry out esterification reaction; carrying out esterification reaction; controlling the esterification temperature at 230°C-250°C, the esterification pressure at 0.4 MPa, and the esterification time at 3 h.

[0058] (3) After the esterification is completed, tetrabutyl titanate and a catalyst dispersion liquid accounting for 7 ppm of the total polyester (the catalyst content is controlled to be 2000 ppm of the total polyester).

[0059] (4) After stirring evenly, perform low vacuum pre-shrinkage reaction, control the pre-shrinkage temperature at 250°C-280°C, slowly control the vacuum degree to 1.5kPa, and pre-shrinkage time is about 50 minutes to discharge excess diol.

[0060] (5) After the pre-shrinkage is completed, the high vacuum final shrinkage reaction is carried out, the polycondensation temperature is controlled at 270°C-285°C, the polycondensation vacuum is controlled at 200 Pa, and the polycondensation time is about 1.5 hours to obtain a product melt. The melt is then allowed to stand, discharged, and pelletized to obtain halogen-free and antimony-free flame-retardant polyester chips.

[0061] (6) Preparation of composite halogen-free and antimony-free flame-retardant polyester injection molding strips: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried under vacuum at 100° C. and injection molded; an oxygen index test is performed in accordance with the requirements of the national standard GB / T2406-2009.

[0062] (7) Preparation of halogen-free and antimony-free flame-retardant polyester fiber: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried according to the following conditions: first, under vacuum conditions, the temperature is raised to 70°C and dried for 2 hours, then kept at 70°C for 2 hours, then the temperature is raised to 110°C and dried for 2 hours, and the drying is continued at 110°C for 9 hours. After the drying is completed, the halogen-free and antimony-free flame-retardant polyester fiber is spun.

[0063] Example 3: A composite halogen-free and antimony-free flame-retardant polyester chip, the preparation method of which comprises the following steps: (1) Preparation of catalyst promoter dispersion: A certain amount of catalyst promoter magnesium hydroxide was added to a mortar and ground in a clockwise direction for 10 minutes; the ground catalyst promoter was placed in a grinder and ground for 5 minutes. A certain amount of liquid nitrogen was added during the grinding to prevent high temperature from destroying the chemical properties of the catalyst promoter. After grinding to D90≤≤1 μm, it was mixed with ethylene glycol in a ratio of 1:9 and ground in a grinder to obtain a catalyst promoter dispersion.

[0064] (2) Adding terephthalic acid, diol (alcohol-acid molar ratio 1:1.3), and flame retardant esterification liquid (phosphorus content is controlled at 6500 ppm of the final polyester product) into the reactor to carry out esterification reaction; the esterification temperature is controlled at 230°C-250°C, the esterification pressure is controlled at 0.4 MPa, and the esterification time is controlled at 3 h.

[0065] (3) After the esterification is completed, tetrabutyl titanate and a catalyst dispersion liquid accounting for 7 ppm of the total polyester (the catalyst content is controlled to be 4000 ppm of the total polyester).

[0066] (4) After stirring evenly, perform low vacuum pre-shrinkage reaction, control the pre-shrinkage temperature at 250°C-280°C, slowly control the vacuum degree to 1.5kPa, and pre-shrinkage time is about 50 minutes to discharge excess diol.

[0067] (5) After the pre-shrinkage is completed, the high vacuum final shrinkage reaction is carried out, the polycondensation temperature is controlled at 270°C-285°C, the polycondensation vacuum is controlled at 200 Pa, and the polycondensation time is about 1.5 hours to obtain a product melt. The melt is then allowed to stand, discharged, and pelletized to obtain halogen-free and antimony-free flame-retardant polyester chips.

[0068] (6) Preparation of composite halogen-free and antimony-free flame-retardant polyester injection molding strips: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried under vacuum at 100° C. and injection molded; an oxygen index test is performed in accordance with the requirements of the national standard GB / T2406-2009.

[0069] (7) Preparation of halogen-free and antimony-free flame-retardant polyester fiber: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried according to the following conditions: first, under vacuum conditions, the temperature is raised to 70°C and dried for 2 hours, then kept at 70°C for 2 hours, then the temperature is raised to 110°C and dried for 2 hours, and the drying is continued at 110°C for 9 hours. After the drying is completed, the halogen-free and antimony-free flame-retardant polyester fiber is spun.

[0070] Example 4: A composite halogen-free and antimony-free flame-retardant polyester chip, the preparation method of which comprises the following steps: (1) Preparation of catalyst promoter dispersion: A certain amount of catalyst promoter magnesium hydroxide was added to a mortar and ground in a clockwise direction for 10 minutes; the ground catalyst promoter was placed in a grinder and ground for 5 minutes. A certain amount of liquid nitrogen was added during the grinding to prevent high temperature from destroying the chemical properties of the catalyst promoter. After grinding to D90≤≤1 μm, it was mixed with ethylene glycol in a ratio of 1:9 and ground in a grinder to obtain a catalyst promoter dispersion.

[0071] (2) Add terephthalic acid, diol (alcohol-acid molar ratio 1:1.3), and flame retardant esterification liquid (phosphorus content is controlled at 6500 ppm of the final polyester product) into the reactor to carry out esterification reaction; the esterification temperature is controlled at 230℃-250℃, the esterification pressure is controlled at 0.4Mpa, and the esterification time is controlled at 3h.

[0072] (3) After the esterification is completed, tetrabutyl titanate and a catalyst dispersion liquid accounting for 7 ppm of the total polyester (the catalyst content is controlled to be 6000 ppm of the total polyester).

[0073] (4) After stirring evenly, perform low vacuum pre-shrinkage reaction, control the pre-shrinkage temperature at 250°C-280°C, slowly control the vacuum degree to 1.5kPa, and pre-shrinkage time is about 50 minutes to discharge excess diol.

[0074] (5) After the pre-shrinkage is completed, the high vacuum final shrinkage reaction is carried out, the polycondensation temperature is controlled at 270°C-285°C, the polycondensation vacuum is controlled at 200 Pa, and the polycondensation time is about 1.5 hours to obtain a product melt. The melt is then allowed to stand, discharged, and pelletized to obtain halogen-free and antimony-free flame-retardant polyester chips.

[0075] (6) Preparation of composite halogen-free and antimony-free flame-retardant polyester injection molding strips: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried under vacuum at 100° C. and injection molded; an oxygen index test is performed in accordance with the requirements of the national standard GB / T2406-2009.

[0076] (7) Preparation of halogen-free and antimony-free flame-retardant polyester fiber: The halogen-free and antimony-free flame-retardant polyester chips prepared in step (5) are dried according to the following conditions: first, under vacuum conditions, the temperature is raised to 70°C and dried for 2 hours, then kept at 70°C for 2 hours, then the temperature is raised to 110°C and dried for 2 hours, and the drying is continued at 110°C for 9 hours. After the drying is completed, the halogen-free and antimony-free flame-retardant polyester fiber is spun.

[0077] Comparative Example 1: The difference from Example 1 is that in Comparative Example 1, pure PET resin is prepared without adding any flame retardant component.

[0078] Comparative Example 2: The preparation method of the composite material of Comparative Example 2 is the same as that of Example 1, except that the catalyst auxiliary agent magnesium hydroxide in step (3) of Example 1 is not added in Comparative Example 2.

[0079] Comparative Example 3: Comparative Example 3 is the same as the preparation method of the composite material in Example 1, except that the amount of magnesium hydroxide added as the catalyst aid in step (3) in Example 1 is controlled to be 100 ppm.

[0080] Comparative Example 4: Comparative Example 4 is the same as the preparation method of the composite material in Example 1, except that the amount of the catalyst auxiliary agent magnesium hydroxide added in step (3) of Example 1 in Comparative Example 3 is controlled to be 20,000 ppm.

[0081] Comparative Example 5: The difference from Example 4 is that no flame retardant esterification liquid is added, and only tetrabutyl titanate (7 ppm of the total polyester) and catalyst auxiliary magnesium hydroxide (6000 ppm) are added.

[0082] Comparative Example 6: The difference from Example 4 is that no titanium catalyst is added, ethylene glycol antimony accounting for 250 ppm of the total polyester amount is added as a catalyst in step (3), and no catalyst auxiliary magnesium hydroxide is added to prepare conventional flame-retardant polyester chips.

[0083] Comparative Example 7: The preparation method of the composite material of Comparative Example 7 is the same as that of Example 4, except that the catalyst auxiliary agent added in step (3) of Example 4 in Comparative Example 7 is zinc oxide dispersion, and the addition amount is controlled to be 6000 ppm.

[0084] Performance Testing The polyesters prepared in the examples and comparative examples were tested for their properties according to GB / T14189-2008, GBT 2408-2008, GBT 5454-1997, and FZ / T 50021. The results are shown in Tables 1 and 2.

[0085] Table 1: Color value results Comparison of Examples 1-4 with Comparative Example 2 reveals that, under the same titanium catalyst conditions, increasing the amount of magnesium hydroxide added improves the b value of the antimony-free flame-retardant polyester chips. Furthermore, comparison of Example 1 with Comparative Example 3 reveals that when insufficient magnesium hydroxide is added, the color value of the chips improves only slightly. Furthermore, comparison of Example 1 with Comparative Example 4 reveals that when excessive magnesium hydroxide is added, crosslinking is severe during polymerization, resulting in high apparent viscosity, low intrinsic viscosity, and poor chip performance. From the comparison between Example 1 and Comparative Example 7, it can be found that when zinc oxide is used as the catalyst auxiliary agent, the color value of the slices is limitedly improved and the viscosity of the slices is relatively low.

[0086] Table 2: Flame retardant performance results Comparison of Examples 1-4 with Comparative Example 2 shows that the flame retardancy of the slices gradually improves with increasing addition of magnesium hydroxide. Furthermore, comparison of Example 4 with Comparative Example 2 shows that the addition of magnesium hydroxide improves the flame retardancy of the slices. Comparison of Example 4 with Comparative Example 6 shows that, compared with conventional flame retardants, the addition of magnesium hydroxide can effectively reduce the number of melt droplets. Comparison of Example 4 with Comparative Example 7 shows that the selection of magnesium hydroxide as a catalyst enhances the flame retardancy of polyester better than zinc oxide.

[0087] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0088] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing halogen-free and antimony-free flame-retardant polyester, characterized in that include: 1) Grinding the catalyst promoter and then pulverizing it under liquid nitrogen cooling; then dispersing the catalyst promoter in ethylene glycol to obtain a catalyst promoter dispersion; The catalyst promoter is one or more of magnesium oxide, magnesium chloride, magnesium hydroxide, magnesium carbonate, magnesium sulfate and magnesium bicarbonate; 2) Mixing and esterifying the dibasic acid, diol and flame retardant diol esterification liquid; 3) After the esterification is completed, a titanium catalyst and a catalyst promoter dispersion are added; after pre-shrinkage and final shrinkage reactions, a halogen-free and antimony-free flame-retardant polyester is obtained.

2. The preparation method according to claim 1, wherein: In step 1), the catalyst aid is magnesium hydroxide.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the D90 of the catalyst promoter in the catalyst promoter dispersion is ≤1 μm.

4. The preparation method according to claim 1 or 2, characterized in that: In step 1), the mass ratio of the catalyst promoter to ethylene glycol is 1:(7-11).

5. The preparation method according to claim 1, wherein: In step 2), The flame retardant in the flame retardant diol esterification liquid is one or both of 2-carboxyethylphenyl hypophosphite or [(6-oxo-6H-dibenzo[1,2]oxaphosphorin-6-yl)methyl]succinic acid; The diol in the flame retardant diol esterification liquid is one or more of ethylene glycol, propylene glycol, butanediol, pentanediol and 1,4-cyclohexanedimethanol.

6. The preparation method according to claim 1 or 5, characterized in that: In step 2), The molar ratio of the dibasic acid to the diol is 1:(1.1-1.4); The amount of the flame retardant diol esterification liquid is 0.5-0.8wt% of the total amount of the polyester product.

7. The preparation method according to claim 1, wherein: In step 2), the reaction temperature of the esterification is 180-250° C., and the reaction pressure is 0-0.40 MPa.

8. The preparation method according to claim 1, wherein: In step 3), The titanium catalyst is one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraisooctyl titanate, methyl titanate, titanium isobutoxide and tetrabutyl titanate; The catalyst accounts for 1-100 ppm of the total amount of polyester product; The catalyst auxiliary accounts for 500-6000ppm of the total amount of the polyester product.

9. The preparation method according to claim 1, wherein: In step 3), The pre-shrinkage reaction temperature is 240-280°C and the pressure is 0.1-3kPa; The final shrinkage reaction temperature is 270-285° C., and the pressure is 30-200 Pa.

10. A halogen-free and antimony-free flame-retardant polyester obtained by the preparation method according to any one of claims 1 to 9.

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