Antimony-free regenerated flame-retardant antibacterial polyester and preparation method thereof

Abstract

The invention relates to the technical field of polyester preparation, and discloses antimony-free regenerated flame-retardant antibacterial polyester and a preparation method thereof.The preparation method comprises the following steps that 1, after waste PET is recycled, regenerated BHET is obtained; (2) the regenerated BHET, a reaction type flame retardant and an organic tin catalyst are stirred and mixed, the reaction type flame retardant is a phosphorus-containing flame retardant, step heating is conducted in the inert gas atmosphere, and flame-retardant functionalized BHET is obtained after reaction; (3) the flame-retardant functionalized BHET, ethylene glycol, a titanium catalyst and a cerium compound are mixed, and the cerium compound is cerium dioxide or cerium hydroxide; then vacuumizing and carrying out condensation polymerization reaction; and after the reaction is finished, standing, cooling and pelletizing. According to the invention, regenerated BHET is used as a raw material, is subjected to flame-retardant functional modification, and then is added together with a cerium compound for condensation polymerization, so that the antimony-free regenerated flame-retardant antibacterial polyester with good hue and spinnability is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyester preparation, and in particular to a non-antimony regenerated flame-retardant antibacterial polyester and a preparation method thereof. BACKGROUND

[0002] Polyethylene terephthalate (polyester, PET) has become the largest output and most widely used fiber material due to its good mechanical properties, heat setting properties and acid and alkali resistance, and the proportion of chemical fibers is more than 80%. However, excessive production capacity and low added value have caused the industry to fall into vicious development. In particular, the flame retardant performance of polyester is poor, with a limiting oxygen index (LOI) of only 21-22%, and it is accompanied by serious dripping and release of toxic smoke during combustion. According to statistics, more than 50% of textile field fires are related to the combustion of PET materials, which cannot meet the flame retardant safety requirements of fields such as construction, medical treatment and transportation. Moreover, the traditional PET synthesis relies on antimony-based catalysts (such as antimony glycol), which have high catalytic efficiency, but antimony as a heavy metal can easily pollute water and soil during production, and the migration of antimony ions during waste PET recycling can also affect subsequent safe application.

[0003] To solve the problem of antimony pollution, the industry has gradually developed non-antimony catalyst systems, among which titanium-based catalysts have become a research hotspot due to their high catalytic activity, low cost and good environmental protection. For example, the patent with publication number CN106700042A discloses a non-antimony environmentally friendly flame-retardant polyester chip and a preparation method thereof, which is prepared by polymerization of ethylene glycol, purified terephthalic acid, flame retardant, dye and titanium-based catalyst, and has a characteristic viscosity of 0.55-0.75 dL / g. A fiber-grade polyester chip with flame retardant properties is obtained, and no harmful heavy metal antimony is released during use. However, the selected flame retardant is metal hypophosphite, which can easily cause performance fluctuations due to uneven dispersion, and has a single function, only achieving flame retardant performance, which cannot meet the multifunctional demand of "flame retardant + antibacterial" in the fields of medical textiles, baby products, etc. Existing antibacterial polyesters rely on silver ions and quaternary ammonium salts, etc. additives, which can easily cause compatibility conflicts when compounded with phosphorus-based flame retardants, resulting in a decrease in antibacterial efficiency or a decrease in flame retardant performance.

[0004] At the same time, the traditional waste PET regeneration process only realizes material recycling through simple hydrolysis-repolymerization, and the reproduct has problems such as wide molecular weight distribution and decreased mechanical properties, and it is difficult to simultaneously realize functional modification such as flame retardance and antibacterial property. BHET is a key product of the waste PET regeneration process, which can be used as an ideal functional carrier, but most flame retardants are directly added to the BHET polymerization system, which cannot realize uniform grafting at the molecular level, resulting in uneven distribution of functional groups in the subsequent polymerization process, and poor performance stability of the end product. SUMMARY

[0005] In order to solve the above technical problems, the application provides a kind of antimony-free regenerated flame-retardant antibacterial polyester and its preparation method, by adding flame-retardant functional regenerated BHET and modified auxiliary agent (cerium compound), reduce the side reaction of titanium catalyst, at the same time, metal elements in modified auxiliary agent have antibacterial function, antimony-free regenerated flame-retardant antibacterial polyester with good color and spinnability is prepared, which is safe and environmentally friendly.

[0006] The object of the application is achieved by the following technical solutions: In the first aspect, the application provides a preparation method of antimony-free regenerated flame-retardant antibacterial polyester, comprising the following steps: (1) after waste PET is recycled, regenerated BHET is obtained; (2) regenerated BHET, reaction type flame retardant and organic tin catalyst are stirred and mixed, wherein the reaction type flame retardant is phosphorus-containing flame retardant, and the flame-retardant functional BHET is obtained after stepwise heating in inert gas atmosphere and reaction; (3) flame-retardant functional BHET, ethylene glycol, titanium catalyst and cerium compound are mixed, wherein the cerium compound is cerium dioxide or cerium hydroxide, and the mass ratio of cerium element in cerium compound to phosphorus element in flame-retardant functional BHET is 0.75-1:1; then vacuumizing is carried out, and polycondensation reaction is carried out; after reaction, standing, cooling and granulation are carried out.

[0007] As preferred, step (1) comprises the following specific steps: S1, after waste PET is cleaned and impurities are removed, it is broken into particles and vacuum dried; S2, the dried particles, ethylene glycol and alcoholysis catalyst are stirred and mixed, and stirred reaction is carried out in nitrogen atmosphere; S3, after reaction is completed, cooling to room temperature is carried out, filtration is carried out, and BHET crude product is obtained; S4, the BHET crude product is dissolved in water, decolorizing agent is added for decolorization, and the filtrate after filtration is recrystallized, dried, and regenerated BHET is obtained.

[0008] As preferred, in S1, the particle size of the particles is 3-5mm; the temperature of vacuum drying is 120-140℃, and the time is 4-8h.

[0009] As preferred, in S2, the mass ratio of the dried particles to ethylene glycol is 1:2-5; the addition amount of the alcoholysis catalyst is 0.4-0.6% of the mass of the dried particles; the alcoholysis catalyst is zinc acetate; the temperature of stirring reaction is 190-200℃, and the time is 2-4h.

[0010] Preferably, in step S4, the mass ratio of the crude BHET product to water is 1:10-20; the decolorizing agent is activated carbon; the amount of the decolorizing agent added is 0.1-0.2% of the mass of the crude BHET product; and the drying temperature is 50-70℃, and the time is 20-24h.

[0011] Preferably, in step (2), the reactive flame retardant is 2-carboxyethylphenyl hypophosphite (CEPPA) and / or [(6-oxo-6H-dibenzo[C,E][1,2]oxophosphoric acid-6-yl)methyl]succinic acid (DDP).

[0012] Preferably, in step (2), the amount of reactive flame retardant added is 3-7% of the mass of BHET; the amount of phosphorus added in the reactive flame retardant is 5000-10000 ppm of the mass of flame-retardant functionalized BHET.

[0013] Preferably, in step (2), the organotin compound is stannous octoate and / or stannous isooctanoate; the amount of the organotin catalyst added is 0.1-0.2% of the mass of BHET.

[0014] Preferably, in step (2), the step heating conditions are: first heat to 170-180℃ and react for 1-2 h, then heat to 195-200℃ and react for 2-3 h.

[0015] Esterification is an exothermic reaction. Excessively high temperatures will inhibit the reaction from proceeding in the forward direction. Therefore, it is necessary to hold the esterification at a low temperature to remove the generated moisture before raising the temperature to further increase the esterification rate.

[0016] As a preferred option, in step (2), after the stepwise heating reaction is completed, the crude product is dissolved in an aqueous ethanol solution, filtered to obtain a clear liquid, recrystallized several times and then dried to obtain flame-retardant functionalized BHET.

[0017] Preferably, the mass ratio of ethanol to water in the ethanol-water solution is 1:10-20; the drying is vacuum drying at a temperature of 50-70°C for 20-24 hours.

[0018] Preferably, in step (3), the amount of ethylene glycol added is 2-3 times the mass of the reactive flame retardant in the flame-retardant functionalized BHET.

[0019] Preferably, in step (3), the titanium-based catalyst is an inorganic salt or complex of titanium.

[0020] Preferably, in step (3), the titanium-based catalyst includes one or more of potassium fluorotitanate, potassium titanium oxalate, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and tetraisooctyl titanate.

[0021] Preferably, in step (3), the amount of titanium catalyst added is 5-20 ppm based on the mass of titanium as a percentage of the theoretical amount of polyester produced.

[0022] Preferably, in step (3), the polycondensation reaction includes a pre-condensation reaction and a final condensation reaction. The temperature of the pre-condensation reaction is 250-280℃ and the pressure is 100-1000Pa. The temperature of the final condensation reaction is 260-290℃ and the pressure is 20-100Pa.

[0023] Secondly, the present invention also provides an antimony-free recycled flame-retardant and antibacterial polyester prepared by the above preparation method.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Using recycled BHET as raw material to prepare polyester can realize a closed loop of recycling of waste polyester from material-monomer-material; (2) Introducing cerium compounds as modifiers, cerium ions can preferentially interact with the active end groups of BHET to form a stable complex structure, and can effectively remove thermal oxidative free radicals through their unique redox properties, significantly inhibiting the yellowing tendency of BHET in preheating and the early stage of reaction, laying the foundation for obtaining polyester products with high whiteness and excellent color value. (3) Pre-esterifying reactive phosphorus flame retardants with BHET can increase the heat resistance temperature of the flame retardants, reduce thermal decomposition during polymerization, and improve the uniformity of distribution in polyester. Moreover, cerium compounds can exhibit excellent synergistic flame retardant effects with flame retardants, and can significantly promote the cross-linking of polyester matrix into carbon, thereby forming a dense protective layer. (4) Using titanium-based catalysts as polycondensation catalysts avoids pollution from heavy metal antimony in the upstream and downstream of the polyester industry, making it safe, non-toxic, and environmentally friendly. At the same time, during the polycondensation process, cerium compounds participate in and optimize the titanium-phosphorus coordination environment, reducing side reactions. The synergistic system formed by cerium compounds and titanium catalysts can further improve polymerization efficiency and shorten the production cycle. (5) Tetravalent cerium has oxidizing properties and significant antibacterial effects. Through the continuous release of cerium ions, the induction of reactive oxygen species (ROS) bursts and the inhibition of key microbial enzyme activities, polyester products are endowed with long-lasting antibacterial ability against Gram-positive and Gram-negative bacteria. Detailed Implementation

[0025] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] In a specific embodiment of the present invention, the preparation of regenerated BHET includes the following steps: S1. After cleaning and removing impurities from waste PET, crush it into 3-5mm particles and dry it in a vacuum oven at 130℃ for 6 hours to obtain dried PET particles. S2. Add 1000g of dried granules, 2500g of ethylene glycol and 5g of alcoholysis catalyst (zinc acetate) to the reactor and stir and mix at a stirring speed of 150rpm. Perform three purging operations to maintain a nitrogen atmosphere in the reactor. Turn on the heating and set the temperature to 195℃. Stir and react for 3 hours. S3. After the reaction is complete, allow it to cool naturally to room temperature and filter it under vacuum using a Buchner funnel to obtain the crude BHET product. S4. Dissolve 100g of crude BHET product in 2000g of deionized water, heat until completely dissolved, add 0.1g of decolorizing agent (activated carbon) for decolorization, filter while hot to obtain filtrate, recrystallize three times in deionized water according to the same mass ratio, and dry thoroughly in a vacuum oven to obtain regenerated BHET.

[0027] Example 1 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0028] Example 2 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.75:1, and the amount of cerium added is 5625ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0029] Example 3 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 1:1, and the amount of cerium added is 7500ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0030] Example 4 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 3.3% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 5000ppm), 52.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 4500ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0031] Example 5 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 6.7% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 10000ppm), 106.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 9000ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0032] Example 6 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, potassium titanium oxalate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0033] Example 7 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetramethyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0034] Example 8 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 170℃ for 1 h, and then heated to 195℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 280℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 290℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0035] Example 9 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (DDP) and organotin catalyst (stannous octoate) were added to the reactor. The amount of DDP added was 7.9% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 124.7g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0036] Example 10 (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium hydroxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and slurried for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0037] Comparative Example 1 The difference from Example 1 is that no cerium compound is added.

[0038] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol and tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain polyester chips.

[0039] Comparative Example 2 The difference from Example 1 is that the phosphorus content and cerium / phosphorus ratio are not within the optimal range.

[0040] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 2.7% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 4000ppm), 42.9g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 1.1:1, and the amount of cerium added is 4400ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled, and granulated to obtain polyester chips.

[0041] Comparative Example 3 The difference from Example 1 is that the phosphorus content and cerium / phosphorus ratio are not within the optimal range.

[0042] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 8% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 12000ppm), 127.0g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.7:1, and the amount of cerium added is 8400ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain polyester chips.

[0043] Comparative Example 4 The difference from Example 1 is that an antimony-based catalyst was used to prepare the polyester.

[0044] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was first carried out at 180℃ for 1 h, and then heated to 200℃ for 2 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, antimony glycol (antimony content is 200ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain polyester chips.

[0045] Comparative Example 5 The difference from Example 1 is that BHET was not flame-retardantized, and CEPPA was directly added to the polyester synthesis process.

[0046] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) 749.6g BHET, 39.6g CEPPA (maintaining a polyester phosphorus content of 7500ppm), 79.4g ethylene glycol, tetrabutyl titanate (titanium content of 7ppm of the theoretical polyester production amount) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization reactor and slurried for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled, and granulated to obtain polyester chips.

[0047] Comparative Example 6 The difference from Example 1 is that step (2) does not use a stepped heating method.

[0048] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate, 0.1% of the mass of BHET) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET. The stirring speed was set to 150 rpm. The nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out by step heating. The reaction was carried out at 180℃ for 3 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0049] Comparative Example 7 The difference from Example 1 is that step (2) does not use a stepped heating method.

[0050] (1) Waste PET is recycled and processed to obtain recycled BHET; (2) Regenerated BHET, reactive flame retardant (CEPPA) and organotin catalyst (stannous octoate) were added to the reactor. The amount of CEPPA added was 5% of the mass of BHET and the amount of stannous octoate added was 0.1% of the mass of BHET. The stirring speed was set to 150 rpm, and the nitrogen atmosphere was ensured by three gas exchanges. The reaction was carried out at 200℃ for 3 h to obtain crude product. The crude product was dissolved in an ethanol aqueous solution (the mass ratio of ethanol to water was 1:15), filtered while hot, recrystallized three times and dried to obtain flame-retardant functionalized BHET. (3) 789.1g of flame-retardant functionalized BHET (phosphorus content 7500ppm), 79.4g of ethylene glycol, tetrabutyl titanate (titanium content is 7ppm of the theoretical amount of polyester) and cerium dioxide (the mass ratio of cerium to phosphorus is 0.9:1, and the amount of cerium added is 6750ppm) were added to the polymerization kettle and pulped for 10min. The pre-condensation reaction was carried out at 260℃ and 200Pa. After the reaction was carried out for 50min, the final condensation reaction was carried out at 275℃ and 50Pa for 80min. After the reaction was completed, the mixture was allowed to stand, cooled and granulated to obtain antimony-free recycled flame-retardant and antibacterial polyester chips.

[0051] Polyester chips were dried in a vacuum drum dryer at 120°C for 12 hours. The dried chips were then used to prepare test samples using an injection molding machine at 260°C. The dried chips were then spun using a spinning machine at 278°C, with a cooling air temperature of 22°C, an oiling rate of 1.0 wt%, and a spinning specification of 83 dtex / 48f to obtain polyester fibers.

[0052] The testing methods used are as follows: 1. The intrinsic viscosity of the chips was tested according to GB / T 14190-2017 "Test Method for Fiber Grade Polyester (PET) Chips"; 2. The vertical burning of the specimens was performed according to GB / T 2408-2021 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods"; 3. The limiting oxygen index of the fiber was tested according to FZ / T 50017-2011 "Test Method for Flame Retardant Properties of Polyester Fiber - Oxygen Index Method"; 4. The antibacterial performance test shall be conducted in accordance with GB / T 20944.3-2008 "Evaluation of antibacterial properties of textiles - Part 3: Vibration method".

[0053] Table 1

[0054] As can be seen from the data in Table 1: (1) Compared with Comparative Example 1, the polyesters of Examples 1-3 have added cerium compounds. Cerium can replace titanium to form complexes with phosphorus, reducing the side reactions of titanium catalysts. Their b values ​​are all lower than 10, and the color of the slices is good. At the same time, after adding cerium compounds, the number of vertical burning droplets is greatly reduced, which improves the flame retardant performance. The antibacterial results show that after adding cerium compounds, the polyester has good antibacterial effects against Escherichia coli and Staphylococcus aureus, with inhibition rates of >90%.

[0055] (2) As can be seen from Examples 1, 5, Comparative Examples 2 and 3, the polyester still has good flame retardant effect within a certain range of phosphorus and cerium content, with a limiting oxygen index > 28%. However, excessively high or low addition amounts will cause the color of the chips to deteriorate (b value > 10) or the limiting oxygen index to fail to meet the standard (LOI < 28%).

[0056] (3) Compared with Comparative Example 4, Examples 6-8, 9, and 10-11 show that the remaining titanium-based catalysts, phosphorus-based flame retardants and cerium compounds listed in this invention can achieve the performance and various indicators of conventional antimony-based polyesters.

[0057] (4) As can be seen from Example 1 and Comparative Example 5, if BHET flame-retardant functionalized repolymerization is not used, but CEPPA is directly added to the polymerization reaction process, the color value of the flame-retardant polyester will deteriorate due to the thermal decomposition of CEPPA (b value > 15), and the flame retardant lost due to thermal decomposition will also lead to a deterioration in the overall flame retardant effect (LOI < 30%).

[0058] (5) As can be seen from Examples 1, 6, and 7, if the stepwise heating is not used in the preparation of flame-retardant functionalized BHET, the degree of esterification will be too high or too low, which will affect the subsequent polyester polycondensation process. In Comparative Example 6, the degree of esterification is too low, the acid value is too high, the polyester chips are easily degraded, and the dropleting is aggravated; in Comparative Example 7, the degree of esterification is too high, the acid value is too low, the reaction rate is slow, the polyester viscosity is too low, which will lead to poor spinning effect and affect the strength and yield of the fiber.

[0059] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing antimony-free recycled flame-retardant and antibacterial polyester, characterized in that, Includes the following steps: (1) Waste PET is recycled and processed to obtain recycled BHET; (2) The regenerated BHET, reactive flame retardant and organotin catalyst are stirred and mixed, wherein the reactive flame retardant is a phosphorus-containing flame retardant. The temperature is increased stepwise under an inert gas atmosphere, and flame-retardant functionalized BHET is obtained after the reaction. (3) Mix flame-retardant functionalized BHET, ethylene glycol, titanium catalyst and cerium compound, wherein the cerium compound is cerium dioxide or cerium hydroxide, and the mass ratio of cerium element in the cerium compound to phosphorus element in the flame-retardant functionalized BHET is 0.75-1:1; then vacuum and carry out polycondensation reaction; after the reaction is completed, let stand, cool and granulate.

2. The preparation method of the antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, characterized in that, In step (2), the reactive flame retardant is 2-carboxyethylphenyl hypophosphite and / or [(6-oxo-6H-dibenzo[C,E][1,2]oxophosphoric acid-6-yl)methyl]succinic acid; the amount of the reactive flame retardant added is 3-7% of the mass of BHET.

3. The method for preparing antimony-free recycled flame-retardant and antibacterial polyester according to claim 1 or 2, characterized in that, In step (2), the organotin compound is stannous octoate and / or stannous isooctanoate; the amount of organotin catalyst added is 0.1-0.2% of the mass of BHET.

4. The preparation method of the antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, characterized in that, In step (2), the step heating conditions are: first heat to 170-180℃ and react for 1-2 h, then heat to 195-200℃ and react for 2-3 h.

5. The method for preparing antimony-free recycled flame-retardant and antibacterial polyester according to claim 1 or 4, characterized in that, In step (2), after the reaction is completed by step heating, the crude product is dissolved in an aqueous ethanol solution, filtered to obtain a clear liquid, recrystallized several times and then dried to obtain flame-retardant functionalized BHET.

6. The preparation method of the antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, characterized in that, In step (3), the amount of ethylene glycol added is 2-3 times the mass of the reactive flame retardant in the flame-retardant functionalized BHET.

7. The preparation method of the antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, characterized in that, In step (3), the amount of titanium catalyst added is 5-20 ppm based on the mass of titanium as a percentage of the theoretical amount of polyester produced.

8. The method for preparing antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, 6, or 7, characterized in that, In step (3), the titanium-based catalyst is an inorganic salt or complex of titanium.

9. The method for preparing antimony-free recycled flame-retardant and antibacterial polyester according to claim 1, 6, or 7, characterized in that, In step (3), the polycondensation reaction includes a pre-condensation reaction and a final condensation reaction. The temperature of the pre-condensation reaction is 250-280℃ and the pressure is 100-1000Pa. The temperature of the final condensation reaction is 260-290℃ and the pressure is 20-100Pa.

10. An antimony-free recycled flame-retardant and antibacterial polyester prepared by the preparation method according to any one of claims 1-9.

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