Polyelemental integrated flame retardant containing schiff base structure and flame-retardant polyester prepared by using same

Abstract

The application provides a multi-element integrated flame retardant containing a Schiff base structure (BNSi), and a flame-retardant polyester prepared by using the flame retardant. The flame-retardant polyester has improved flame-retardant performance while the mechanical performance is ensured. The multi-element integrated flame retardant containing a Schiff base structure can form a dense carbon layer in the combustion process, plays a protective barrier role, inhibits the release of heat, smoke and toxic gas, and reduces the fire risk of the polyester.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polyester flame retardant, and particularly relates to a multi-element integrated flame retardant containing Schiff base structure and polyester prepared by using the flame retardant. BACKGROUND

[0002] Polyester fiber is one of important varieties of synthetic fibers. The polyester fiber has many advantages, such as high strength, good elasticity, wear resistance, heat resistance, light resistance, corrosion resistance, fast drying speed, etc., and is widely used in textile products. Since its advent, the polyester fiber has developed rapidly. At present, the use amount of the polyester fiber accounts for one third of the total amount of textile fibers in the world, 60% of the use amount of synthetic fibers in the world, and 50% of the processing amount of textile fibers in China.

[0003] However, since the limiting oxygen index of synthetic polyester fiber is low, it is easy to burn, and the research on its flame retardance has become a global concern. Adding flame retardant to synthetic fiber to make it have flame retardance is the main method to solve the flammability problem of synthetic fiber at present. Mainly adding monomers containing flame-retardant elements in the reaction to form copolymers; in addition, blending flame-retardant functional additives with polymer melt or solution to spin flame-retardant fiber; or coating finishing the fiber or fabric, etc.

[0004] Among the flame retardants, the amount of smoke released after adding boron-based flame retardant is small, the amount of toxic gas released is reduced, and the water released when heated can dilute the combustible gas to retard flame. However, the amount is large, which seriously affects the mechanical properties and thermal stability of the material.

[0005] The halogen-based flame retardant has large output, small addition amount, good flame-retardant effect, low price, good compatibility and stability. However, the halogen-based flame retardant releases a large amount of toxic gas when burning, and countries are trying to reduce or even avoid the use of halogen-based flame retardant.

[0006] At present, the use of flame retardant also affects the mechanical properties of polyester, reduces the spinnability, and reduces the softness of the fiber, which seriously affects the application of polyester fiber in textile products. Therefore, further research on the flame-retardant method of polyester is needed to obtain good flame retardance, anti-dripping, good spinnability, to meet the needs of people's life and production. SUMMARY

[0007] To solve the above problems, the application provides a polyhedral oligomeric silsesquioxane with an imine group as a flame retardant, which is added into PET (polyethylene terephthalate) through melt blending. When the obtained flame-retardant polyester burns, the flame retardant will undergo crosslinking reaction to form a stable six-membered ring, thereby converting into a carbon layer covering the surface of the matrix to achieve the flame-retardant effect. The thermal stability of the flame-retardant polyester is enhanced, the amount of residual carbon after burning is increased, the carbon layer is more compact, the release of smoke is effectively inhibited during the combustion process, the flame-retardant polyester has excellent spinnability, and the mechanical properties are maintained to a certain extent, thereby completing the application.

[0008] The first aspect of the application aims to provide a multi-element integrated flame retardant containing a Schiff base structure, which is:

[0009]

[0010] wherein R0 is an alkyl group containing a cage-type polyhedral oligomeric silsesquioxane group.

[0011] The second aspect of the application aims to provide a preparation method of the multi-element integrated flame retardant containing a Schiff base structure, which is prepared by reacting a raw material comprising an amino-containing polyhedral oligomeric silsesquioxane and 4-aldehyde benzene boronic acid.

[0012] The third aspect of the application aims to provide a flame-retardant polyester, which is prepared by adding the multi-element integrated flame retardant containing a Schiff base structure into polyethylene terephthalate (PET) and melt blending.

[0013] The fourth aspect of the application aims to provide a preparation method of the flame-retardant polyester, which is prepared by adding the multi-element integrated flame retardant containing a Schiff base structure into polyethylene terephthalate (PET) and melt blending.

[0014] The multi-element integrated flame retardant containing a Schiff base structure and the flame-retardant polyester provided by the application have the following beneficial effects:

[0015] (1) The application uses an amino-containing polyhedral oligomeric silsesquioxane and 4-aldehyde benzene boronic acid as raw materials to prepare an imino-containing polyhedral oligomeric silsesquioxane flame retardant. The flame retardant has good thermal stability, and the initial decomposition temperature is higher than the processing temperature of PET, so that a flame-retardant polyester can be prepared by melt blending.

[0016] (2) The multi-element integrated flame retardant containing a Schiff base structure provided in the application can be used for PET flame retardation, can crosslink during combustion to form a dense carbon layer, plays a protective barrier role during the combustion process, inhibits the release of heat, smoke and toxic gases, and improves the flame-retardant performance of the polyester.

[0017] (3) The flame-retardant polyester obtained by using the multi-element integrated flame-retardant agent containing a Schiff base structure in the application has high carbon formation amount, improved initial decomposition temperature, effectively delayed heat release and small molecule diffusion during combustion, so that the flame-retardant performance is improved. And the flame-retardant polyester in the application has good mechanical properties and spinning properties, which can meet the needs of people in production and life. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The nuclear magnetic spectrum of the multi-element integrated flame-retardant agent A containing a Schiff base structure prepared in Example 1 of the application is shown;

[0019] Figure 2 The infrared spectrum of the multi-element integrated flame-retardant agent A containing a Schiff base structure prepared in Example 1 of the application is shown;

[0020] Figure 3 The thermogravimetric analysis diagram of 4-formylphenylboronic acid, NH2-POSS and the multi-element integrated flame-retardant agent A containing a Schiff base structure in Example 1 of the application is shown;

[0021] Figure 4 The TG-DSC test diagram of pure PET in Comparative Example 1 and PET-3BNSi in Example 2 of the application is shown;

[0022] Figure 5 The HRR heat release rate-time curve of pure PET in Comparative Example 1 and the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2 of the application is shown;

[0023] Figure 6 The THR curve of pure PET in Comparative Example 1 and the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2 of the application is shown. DETAILED DESCRIPTION

[0024] The application will be described in detail below through specific embodiments, and the features and advantages of the application will become clearer and more explicit with these descriptions.

[0025] The application provides a multi-element integrated flame-retardant agent containing a Schiff base structure, which is:

[0026]

[0027] R0 is an alkyl group containing a cage polyhedral oligomeric silsesquioxane substituent group, the cage polyhedral oligomeric silsesquioxane substituent group being connected to N through an alkylene group, the alkylene group being selected from alkylene groups containing 1-6 carbon atoms, preferably alkylene groups containing 2-4 carbon atoms, more preferably propylene.

[0028] Preferably, the multi-element integrated flame retardant containing a Schiff base structure is:

[0029]

[0030] R is selected from alkyl groups, preferably from alkyl groups containing 1-6 carbon atoms, more preferably from alkyl groups containing 2-5 carbon atoms, such as isobutyl (— CH2CH(CH3)CH3).

[0031] The initial decomposition temperature of the multi-element integrated flame retardant containing a Schiff base structure is greater than 280℃, preferably greater than 290℃, more preferably greater than 300℃. The residual solid amount at 700℃ is greater than 30wt%, preferably greater than 35wt%.

[0032] The stability of the carbon layer of the current boron-based flame retardant deteriorates as the temperature increases, which can cause secondary release of heat. In actual application, a single flame retardant not only has a large amount of addition and is difficult to achieve high-efficiency flame retardation, but also affects the mechanical properties of the matrix.

[0033] In the present application, the boron-containing group in the multi-element integrated flame retardant containing a Schiff base structure enables the flame retardant to play a good carbonization effect in the condensed phase, and further play an effective shielding effect in the gas phase and the condensed phase. In addition, compared with the traditional multi-component flame retardant complex, the multi-element integrated flame retardant containing a Schiff base structure in the present application has higher flame retardant efficiency.

[0034] In addition to containing the flame-retardant element N, the Schiff base compound in the flame retardant in the present application has a good fireproof performance of -C=N- in the molecular structure. -C=N- undergoes crosslinking reaction to form a stable polybenzoxazine and a six-membered ring structure of alternating carbon and nitrogen elements when burning, forming a stable carbon layer covering the surface of the polymer, thereby achieving higher flame retardation effect.

[0035] The present application also provides a preparation method of the multi-element integrated flame retardant containing a Schiff base structure, which is prepared by reacting a raw material comprising an amino-containing polyhedral oligomeric silsesquioxane and 4-aldehyde benzene boronic acid.

[0036] The amino-containing polyhedral oligomeric silsesquioxane is selected from amino alkyl cage polyhedral oligomeric silsesquioxanes, wherein the amino alkyl group is selected from amino alkyl groups containing 1-6 carbon atoms, preferably amino alkyl groups containing 2-4 carbon atoms, more preferably amino propyl.

[0037] Preferably, the aminoalkyl cage polyhedral oligomeric silsesquioxane is of formula

[0038]

[0039] wherein R is selected from alkyl, preferably from alkyl having carbon number of 1-6, more preferably from alkyl having carbon number of 2-5, such as isobutyl (— CH2CH(CH3)CH3).

[0040] The molar mass ratio of the 4-aldehyde phenylboronic acid to the amino-containing polyhedral oligomeric silsesquioxane is 6.5 mmol:(2.5-10) g, preferably 6.5 mmol:(3.5-8) g, more preferably 6.5 mmol:(4.5-6) g.

[0041] The reaction is carried out under solvent condition, the solvent is selected from one or more of alcohol solvent, ether solvent and aromatic solvent, preferably selected from one or more of alcohol solvent, more preferably one or more of methanol, ethanol, propanol and isopropanol, such as ethanol.

[0042] The molar volume ratio of the 4-aldehyde phenylboronic acid to the solvent is 6.5 mmol:(80-200) mL, preferably 6.5 mmol:(100-180) mL, more preferably 6.5 mmol:(120-160) mL.

[0043] The reaction is carried out under heating condition, the heating temperature is 40-90℃, preferably 45-80℃, more preferably 50-70℃. The reaction time is 3-9h, preferably 4-8h, more preferably 5-7h. The reaction is carried out under protective atmosphere, such as nitrogen or argon atmosphere.

[0044] After the reaction is completed, the solvent is removed, and the product is obtained after washing and drying.

[0045] The present application provides a flame-retardant polyester, which is prepared by adding the multi-element integrated flame retardant containing Schiff base structure to polyethylene terephthalate (PET) and melt blending.

[0046] The mass of the multi-element integrated flame retardant containing Schiff base structure accounts for 0.8%-8% of the total mass of polyethylene terephthalate and the multi-element integrated flame retardant containing Schiff base structure, preferably 2%-7%, more preferably 3%-5%.

[0047] The initial decomposition temperature of the flame-retardant polyester is higher than 362℃, even higher than 370℃.

[0048] The limiting oxygen index of the flame-retardant polyester is greater than 22, even greater than 24, more preferably not less than 27.

[0049] The fire growth rate index FIGRA of the flame-retardant polyester is less than 9, even less than 7.5, more preferably less than 5.5.

[0050] The fire performance index FPI of the flame-retardant polyester is greater than 0.07, even greater than 0.1.

[0051] The tensile strength of the flame-retardant polyester is greater than 45 MPa, even greater than 50 MPa; the elastic modulus is greater than 1000 MPa, even greater than 1100 MPa; and the elongation at break is greater than 200%, even greater than 270%.

[0052] The application also provides a preparation method of the flame-retardant polyester, which comprises adding the multi-element integrated flame retardant containing Schiff base structure into polyethylene terephthalate (PET) to prepare the flame-retardant polyester by melt blending.

[0053] Preferably, the PET is quenched and crushed before being blended with the multi-element integrated flame retardant containing Schiff base structure, so that the two are more uniformly mixed.

[0054] The melt blending temperature is 240-280℃, more preferably 260-270℃.

[0055] The multi-element integrated flame retardant containing Schiff base structure provided by the application can be used for PET flame retardation, has a Schiff base structure in the molecular structure, has multiple flame-retardant elements, and forms an integrated flame-retardant system. 5wt％ 303℃, the C w 36.8% at 700℃, and the thermal stability meets the processing requirements of PET and the carbon residue is high.

[0056] The flame-retardant polyester prepared by using the same can undergo crosslinking reaction in the range of 350-400℃ to form a stable six-membered ring structure, increase the carbon residue at 700℃, and form an effective carbon layer. The heat reduction and smoke suppression are realized, the mechanical properties and spinnability are good, and the application in practical application is facilitated.

[0057] Embodiment

[0058] Embodiment 1

[0059] 0.98g of 4-formylphenylboronic acid and 5.25g of NH2-POSS (produced by Changsha Baxi Instrument Co., Ltd., as shown in formula (I-1)) were added into 150mL of an ethanol solution, and stirred to be fully dissolved and transferred into a reaction bottle. After vacuumizing, nitrogen was filled, and the operation was repeated three times to maintain a nitrogen atmosphere in the bottle. Under stirring, the temperature was increased to 60℃ for heating reflux reaction for 6h.

[0060] After the reaction is complete, the reaction solution is transferred to a round-bottom flask and placed in a rotary evaporator. At 45°C, excess solvent is evaporated off. The solution is washed three times with methanol, and the supernatant is removed by centrifugation to obtain a pale yellow solid. The solid is placed in a vacuum oven at 130°C and dried for 12 hours. After cooling to room temperature, a pale yellow powder is obtained, which is a multi-element integrated flame retardant A containing a Schiff base structure (as shown in formula (Ⅱ-1)). The powder is sealed and stored.

[0061]

[0062] Wherein, R is isobutyl (—CH2CH(CH3)CH3).

[0063] use 1 ¹H NMR characterized the chemical environment of the H atom in the multi-element integrated flame retardant A containing a Schiff base structure. The spectrum is shown in Figure 1. Figure 1 As shown, the proton hydrogen in the multi-element integrated flame retardant A containing a Schiff base structure under different chemical environments is mainly: (1) 1.52 ppm is the vibration peak of proton hydrogen on the boron hydroxyl group; (2) 8.02 ppm is the vibration peak of proton hydrogen in the -C=N group of the Schiff base; (3) 0.70 ppm is the vibration peak of proton hydrogen in the methylene group connected to Si on the active side group of NH2-POSS; (4) 1.48 ppm is the vibration peak of proton hydrogen in the methylene group on the active side group of NH2-POSS; (5) 2.82 ppm is the vibration peak of proton hydrogen in the methylene group connected to the nitrogen atom of NH2-POSS; (6), (7), and (8) are the vibration peaks of proton hydrogen on the R group on NH2-POSS; (9) 8.18 ppm is mainly the vibration peak of proton hydrogen on the benzene ring. In summary, the successful synthesis of the multi-element integrated flame retardant A containing a Schiff base structure is demonstrated.

[0064] Example 2

[0065] Terephthalic acid (TPA) (700g, about 4.2mol) and ethylene glycol (EG) (314g, about 5.0mol) were added to a polymerization autoclave and mixed. Under a nitrogen atmosphere, the mixture was heated to 230℃~240℃ to carry out the esterification reaction.

[0066] Then, under a nitrogen atmosphere, 10g of EG, 0.7g of TPI (triphenyl phosphite) and 0.7g of HyMax 1010 (purchased from Shanghai Langyi Functional Materials Co., Ltd., industrial grade) were added to a high-pressure polymerization reactor. The reaction was carried out at 230℃~240℃ under normal pressure for 40 minutes. Then, the temperature was raised to 280℃ and the reaction was carried out under a high vacuum of -101KPa. The stirring power reached the discharge power to complete the polycondensation reaction. The product was then discharged and granulated to obtain PET chips.

[0067] The PET chips were placed in a vacuum drying oven at a temperature of 130°C and dried for 12 hours. The PET chips were first quenched in liquid nitrogen and then crushed by a crusher to mix with the multi-element integrated flame retardant A containing a Schiff base structure prepared in Example 1.

[0068] The temperature of each zone of the twin-screw extruder was set to 270, 265, 265, 265, 265, and 260°C, and the rotation speed of the screw was set to 50 r / min. The mixture of PET and the multi-element integrated flame retardant A containing a Schiff base structure was injection molded by an injection molding machine and a film press to prepare standard samples for subsequent test experiments. The mass fraction of the multi-element integrated flame retardant A containing a Schiff base structure in the mixture was 1wt%, 3wt%, 5wt%, and 7wt%, respectively, and the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi, and PET-7BNSi were obtained.

[0069] Comparative Example

[0070] Comparative Example 1

[0071] Pure PET was processed according to the method in Example 2, except that the multi-element integrated flame retardant A containing a Schiff base structure was not added.

[0072] Experimental Example

[0073] Experimental Example 1

[0074] The 4-formylphenylboronic acid, NH2-POSS, and the multi-element integrated flame retardant A containing a Schiff base structure in Example 1 were tested by infrared spectroscopy, and the test spectrum is shown in Figure 2 .

[0075] As can be seen from Figure 2 , the peak at 2928 cm -1 is the stretching vibration peak of alkyl C-H, and the peak at 1092 cm -1 is the stretching vibration peak of Si-O-Si; the peak at 3312 cm -1 , the peak at 1640 cm -1 , and the peak at 1359 cm -1 are the typical stretching vibration peaks of B-OH, C=O, and B-O on the molecular chain of 4-formylphenylboronic acid; the multi-element integrated flame retardant A containing a Schiff base structure has a C=N stretching vibration peak at 1690 cm -1 , indicating that 4-formylphenylboronic acid and NH2-POSS react to form a Schiff base structure (C=N). In addition, the multi-element integrated flame retardant A containing a Schiff base structure has peaks at 1092 cm -1 and 2928 cm -1stretching vibration peaks of Si-O-Si and substituted alkyl C-H, 3312 cm -1 stretching vibration peak of B-OH, which also indicates the successful synthesis of the multi-element integrated flame retardant A containing the Schiff base structure.

[0076] Experimental Example 2

[0077] Thermogravimetric analysis was performed on 4-formylphenylboronic acid, NH2-POSS and the multi-element integrated flame retardant A containing the Schiff base structure in Example 1, and the thermogravimetric graph is shown in Figure 3 .

[0078] As shown in Figure 3 , the initial decomposition temperature of NH2-POSS is 235°C (T 5％ ), the maximum thermal decomposition temperature (T max ) is 309°C, and the residual carbon at 700°C is 1.4%; the decomposition temperature of 4-formylphenylboronic acid is 281°C, T max is 592°C, the residual solid at 700°C is 62.8%, and it has excellent carbon formation ability. The initial decomposition temperature of the multi-element integrated flame retardant A containing the Schiff base structure is 303°C, T max is 568°C, and the residual solid at 700°C is 36.8%. By comparison, NH2-POSS has a low decomposition temperature and is almost completely decomposed at 700°C, while the thermal stability of the multi-element integrated flame retardant A containing the Schiff base structure is improved, and it can still maintain good stability at the PET processing temperature, and has excellent carbon formation ability when a fire occurs.

[0079] Experimental Example 3

[0080] TG-DSC tests were performed on pure PET in Comparative Example 1 and PET-3BNSi in Example 2, and the test results are shown in Figure 4 .

[0081] The crosslinking behavior of PET-3BNSi was studied by TG-DSC test at a rate of 10°C·min -1 under a nitrogen atmosphere, and the results are shown in Figure 4The DSC curve of pure PET shows no other peak between the melting peak and the decomposition peak, while the DSC curve of PET-3BNSi shows a distinct exothermic peak between the melting peak and the decomposition peak. Pure PET has no exothermic process, and the melting directly decomposes. The special exothermic peak of PET-3BNSi proves that the cross-linking reaction occurs in the range of 350-400°C, and the addition of the multi-element integrated flame retardant A containing Schiff base structure promotes the cross-linking of PET. PET is a linear macromolecule, and it is difficult to occur chemical cross-linking reaction. It is speculated that after the addition of the multi-element integrated flame retardant A containing Schiff base structure, cross-linking reaction occurs due to the presence of -C=N during combustion, forming a stable six-membered ring structure. This structure can be further converted into carbon to cover the surface of the matrix, thereby achieving the effect of flame retardation.

[0082] Experimental Example 4

[0083] The pure PET in Comparative Example 1 was subjected to thermogravimetric analysis under nitrogen and air atmosphere, and the results are shown in Table 1.

[0084] Under nitrogen atmosphere, pure PET and flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi, and PET-7BNSi only have one degradation process. Compared with pure PET, the initial decomposition temperature of PET-3BNSi decreases, which may be due to the fact that the R group on the cage-like silane of the multi-element integrated flame retardant A containing Schiff base structure first breaks down, causing the initial decomposition temperature to advance. Under high temperature conditions, the temperature at the maximum thermal weight loss rate of the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi, and PET-7BNSi slightly increases, and the T max of PET-3BNSi is 439.6°C, which is 2.5°C higher than that of pure PET, and the maximum thermal weight loss rate also decreases from 22.3%·min -1 of PET to 19.6%·min -1, which shows that the addition of the multi-element integrated flame retardant A containing the Schiff base structure improves the thermal stability of PET at high temperature and slows down the thermal decomposition rate of PET. With the increase of the amount of the multi-element integrated flame retardant A containing the Schiff base structure, the carbon residue at 700℃ increases from 8.2% to 11.5%. The increase of the carbon residue is due to the crosslinking reaction of the flame-retardant polyester PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi, which can form a stable crosslinked network structure covering the surface of the substrate, and the cage-like silane degrades into more silicon-containing particles covering the surface of the substrate at high temperature, making the carbon layer more dense. It is well known that the flame retardancy of polymers is closely related to the carbonization capacity, and high carbonization capacity can serve as a physical barrier to prevent materials from being heated and oxygen-deficient, thereby imparting good flame retardancy to the materials.

[0085] In an air atmosphere, the decomposition of pure PET and PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi mainly contains two main stages. After adding the multi-element integrated flame retardant A containing the Schiff base structure, the initial decomposition temperature T 5wt％ is significantly improved compared with pure PET, and PET-3BNSi increases from 362.3℃ to 371.6℃, an increase of 9.3℃. The temperature T max corresponding to the maximum thermal weight loss rate of PET-3BNSi in the second stage is also significantly higher than the corresponding degradation temperature of PET, and the thermal degradation rate R max of PET-3BNSi in the second stage is also significantly lower than that of pure PET, and the carbon residue at 700℃ increases from 0.2% of pure PET to 0.6%, which is mainly because the decomposition products of the multi-element integrated flame retardant A containing the Schiff base structure promote the formation of protective carbon layer covering the surface of the substrate, and finally improve the thermal and oxidative stability of PET.

[0086] Table 1

[0087]

[0088] Experimental Example 5

[0089] The limiting oxygen index LOI and UL-94 of pure PET in Comparative Example 1 and flame-retardant polyester PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2 were tested, and the results are shown in Table 2.

[0090] Table 2

[0091]

[0092]

[0093] From the data in Table 2, it can be seen that as the amount of the multi-element integrated flame retardant A containing a Schiff base structure added increases, the LOI of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi shows a growth trend. When the amount added is 7 wt%, the LOI of PET-7BNSi increases from 22% to 33%, indicating that the multi-element integrated flame retardant A containing a Schiff base structure has excellent flame retardant effect on PET, which is due to the combined effect of multiple elements in the multi-element integrated flame retardant A containing a Schiff base structure during combustion. During the UL-94 test, there is still molten droplet dripping, which ignites the absorbent cotton, and the UL-94 reaches V-2 level. During the UL-94 test, the flame burning time of PET is shortened, because after the cage structure of NH2-POSS is destroyed at high temperature, the melt is covered, the internal afterflame continues to burn, the melt volume becomes larger, and the melt is not carbonized in time, which is easy to fall and ignite the absorbent cotton.

[0094] Experimental Example 6

[0095] The pure PET in Comparative Example 1 was subjected to a cone calorimeter test with the flame retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2. The curves of HRR heat release rate, total heat release (THR) versus time are shown in Figure 5 and Figure 6 The relevant data of heat parameters are shown in Table 3.

[0096] Table 3

[0097]

[0098] Compared with PET, the ignition time (TTI) of PET-1BNSi and PET-3BNSi is slightly extended at a low amount of the multi-element integrated flame retardant A containing a Schiff base structure, but when the amount added is greater than 5 wt%, the TTI is slightly ahead of time. The t-pHRR (peak heat release rate time) of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi is ahead of time compared with pure PET, and the t-pHRR of PET-3BNSi is ahead of time to 97 s, which is due to the fact that the multi-element integrated flame retardant A containing a Schiff base structure accelerates the heat transfer inside the matrix, so the t-pHRR of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi is ahead of time.

[0099] From Figure 5It can be seen that with the addition of the multi-element integrated flame retardant A containing Schiff base structure, the peak type of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi becomes wider and slower, indicating that the addition of the multi-element integrated flame retardant A containing Schiff base structure can effectively delay the release of heat, especially after the addition of 7wt%, the pHRR decreases from 1085.62kW·m -2 to 382.60kW·m -2 , a decrease of 64.8%.

[0100] As can be seen from Table 3, the av-HRR (average heat release rate) decreases from 271.50kW·m -2 to 167.03kW·m -2 , a decrease of 38.5%, indicating that the addition of the multi-element integrated flame retardant A containing Schiff base structure can effectively reduce the heat release, and as the amount of the multi-element integrated flame retardant A containing Schiff base structure increases, the heat release decreases more obviously.

[0101] Figure 6 As can be seen from Table 3, the THR of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi is lower than that of pure PET. According to the data, the THR of PET-3BNSi is 10.4% lower than that of pure PET. According to the curves of HRR and THR, it can be concluded that the multi-element integrated flame retardant A containing Schiff base structure can significantly delay the heat release rate and reduce the total heat release. The multi-element integrated flame retardant A containing Schiff base structure plays a role in promoting carbon in the condensed phase, and forms an insulating carbon layer during the combustion process, effectively blocking the release of heat and delaying the degradation of PET.

[0102] As can be seen from the av-EHC (average effective combustion heat) values in Table 3, after the addition of the multi-element integrated flame retardant A containing Schiff base structure, the av-EHC decreases to different degrees. Compared with PET, PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi decrease by 11.8%, 21.8%, 14.6% and 23.5% respectively. From the analysis of the entire combustion process, combined with the values of HRR, THR and EHC (effective combustion heat), it is shown that the multi-element integrated flame retardant A containing Schiff base structure has a significant delaying effect on the heat release of PET during combustion, forming an effective shielding carbon layer to delay the release of heat and the diffusion of flammable small molecules, mainly showing condensed phase flame retardation.

[0103] Experimental Example 7

[0104] The COP, CO2P, SPR and TSP values of the pure PET in Test Comparative Example 1, the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2 were tested, to obtain PCOP (peak carbon monoxide production), PCO2P (peak carbon dioxide production), PSPR (peak smoke production rate) and TSP (total smoke production) values, as shown in Table 4.

[0105] Compared with the PSPR value of the pure PET, the PSPR values of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi were reduced by 61.3%, 64.9%, 64.9% and 69.9%, respectively, and the carbon layer density increased as the combustion proceeded, which inhibited the release of smoke. In combination with the TSP data, it can be seen that the TSP of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi slightly decreased, and the TSP value of PET-5BNSi increased slightly, but the increase was not large, which was similar to the trend of the THR. This can be due to the fact that, during the combustion process, the carbon layer density gradually increased as the combustion proceeded, but due to the uneven distribution of the flame retardant, the carbon layer barrier was damaged to a certain extent under the condition of continuous heating, so the TSP slightly increased.

[0106] From the CO and CO2 production rates, it can be found that the addition of the multi-element integrated flame retardant A containing the Schiff base structure can reduce the release of CO and CO2. The reduction of CO can reduce the release of toxic gases in the gas phase, and increase the chances of escape in a fire. The reduction of CO2 release indicates that a dense carbon layer is generated during the combustion process, which acts as a protective barrier, inhibits the release of heat, smoke and toxic gases, and reduces the danger of fire.

[0107] Table 4

[0108]

[0109] Experimental Example 8

[0110] The fire growth rate index FIGRA, fire safety performance index FPI and carbon layer shielding effect E of the pure PET in Test Comparative Example 1 and the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2 were calculated. Barrier The results are shown in Table 5.

[0111] From Table 5, the FGI values of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi are reduced to 4.52, 5.13, 3.94 and 3.75 respectively. The size of FPI is related to TTI and pHRR, the delay of TTI and the reduction of pHRR in the initial stage of combustion can lead to the reduction of FPI value, and the results show that FPI value increases with the increase of the amount of the multi-element integrated flame retardant A containing Schiff base structure, indicating that the fire safety index of PET increases after adding the multi-element integrated flame retardant A containing Schiff base structure. Shielding effect E Barrier As can be seen from the table, the percentages of PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi are 47.46%, 52.52%, 60.42% and 64.09% respectively, it can be seen that the multi-element integrated flame retardant A containing Schiff base structure mainly plays a shielding role in the combustion process, and the more the amount, the more obvious the shielding effect, which is mainly due to the synergistic effect of multi-elements in BNSi, which promotes the formation of dense carbon layer, thereby effectively reducing the fire hazard of flame-retardant PET.

[0112] Table 5

[0113] Sample FIGRA FPI E Barrier ]]> Pure PET 9.24 0.058 Blank sample PET-1BNSi 4.52 0.120 47.46％ PET-3BNSi 5.13 0.120 52.52％ PET-5BNSi 3.94 0.127 60.42％ PET-7BNSi 3.75 0.141 64.09％

[0114] Experimental Example 9

[0115] The mechanical properties of pure PET in Comparative Example 1 were tested with the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2, and the tensile strength, elastic modulus and elongation at break were tested by using a universal testing machine, and the results are shown in Table 6.

[0116] From the data in Table 6, compared with pure polyester, the tensile strength increases, and the elastic modulus and elongation at break slightly decrease. The tensile strength of PET-3BNSi is increased to 54.80 MPa, the elastic modulus is 1112.84 MPa, and the elongation at break is 285%, which maintains good mechanical properties.

[0117] Table 6

[0118] Sample Tensile strength (MPa) Elastic modulus (MPa) Elongation at break (%) Pure PET 43.54 1205.98 324％ PET-1BNSi 54.33 1043.46 205％ PET-3BNSi 54.80 1112.84 285％ PET-5BNSi 53.83 1123.84 35％ PET-7BNSi 51.93 1161.21 100％

[0119] Experimental Example 10

[0120] The spinning properties of pure PET in Comparative Example 1 were tested with the flame-retardant polyesters PET-1BNSi, PET-3BNSi, PET-5BNSi and PET-7BNSi in Example 2. The spinning conditions and fiber property test results are shown in Table 7 and Table 8.

[0121] Table 7

[0122]

[0123] Table 8

[0124]

[0125] The present application has been described in detail with specific reference to particular embodiments and / or examples and / or drawings, but it will be understood that these are included for illustrative purposes only and not for purposes of limitation. It will be appreciated that those skilled in the art will be able to devise numerous alternative arrangements, modifications and equivalents without departing from the spirit and scope of the application as defined by the appended claims. The description is thus to be considered in all respects as illustrative and not restrictive.

Claims

1. A multi-element integrated flame retardant containing a Schiff base structure, wherein the multi-element integrated flame retardant containing a Schiff base structure is shown in formula (II): in, R is selected from alkyl groups having 1-6 carbon atoms.

2. The flame retardant according to claim 1, characterized in that, R is an alkyl group containing 2-5 carbon atoms.

3. The flame retardant according to claim 1, characterized in that, The initial decomposition temperature of the multi-element integrated flame retardant containing Schiff base structure is greater than 280℃; its residual solids content at 700℃ is greater than 30wt%.

4. The flame retardant according to claim 3, characterized in that, The initial decomposition temperature of the multi-element integrated flame retardant containing Schiff base structure is greater than 290℃; its residual solids content at 700℃ is greater than 35wt%.

5. The flame retardant according to claim 4, characterized in that, The initial decomposition temperature of the multi-element integrated flame retardant containing Schiff base structure is greater than 300℃.

6. A method for preparing a Schiff base-containing multi-element integrated flame retardant according to any one of claims 1 to 5, characterized in that, It is prepared by reacting amino-containing polyhedral oligomeric silsesquioxanes and 4-aldehyde phenylboronic acid as raw materials. The amino-containing polyhedral oligomeric silsesquioxane is selected from aminoalkyl cage-type polyhedral oligomeric silsesquioxanes, wherein the aminoalkyl group is aminopropyl. The molar ratio of the 4-aldehyde phenylboronic acid to the amino-containing polyhedral oligomeric silsesquioxane is 6.5 mmol:(2.5-10) g.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the 4-aldehyde phenylboronic acid to the amino-containing polyhedral oligomeric silsesquioxane is 6.5 mmol:(3.5-8) g.

8. The preparation method according to claim 7, characterized in that, The molar ratio of the 4-aldehyde phenylboronic acid to the amino-containing polyhedral oligomeric silsesquioxane is 6.5 mmol:(4.5-6) ​​g.

9. A flame-retardant polyester, characterized in that, The flame-retardant polyester is prepared by melt blending a Schiff base-containing multi-element integrated flame retardant as described in any one of claims 1 to 5 into polyethylene terephthalate.

10. The flame-retardant polyester according to claim 9, characterized in that, The mass of the Schiff base-containing multi-element integrated flame retardant accounts for 0.8%-8% of the total mass of polyethylene terephthalate and the Schiff base-containing multi-element integrated flame retardant.

11. The flame-retardant polyester according to claim 10, characterized in that, The mass of the Schiff base-containing multi-element integrated flame retardant accounts for 2%-7% of the total mass of polyethylene terephthalate and the Schiff base-containing multi-element integrated flame retardant.

12. The flame-retardant polyester according to claim 11, characterized in that, The mass of the Schiff base-containing multi-element integrated flame retardant accounts for 3%-5% of the total mass of polyethylene terephthalate and the Schiff base-containing multi-element integrated flame retardant.

13. The flame-retardant polyester according to claim 9, characterized in that, In an air atmosphere, the initial decomposition temperature of the flame-retardant polyester is higher than 362°C.

14. The flame-retardant polyester according to claim 13, characterized in that, In an air atmosphere, the initial decomposition temperature of the flame-retardant polyester is above 370°C.

15. The flame-retardant polyester according to claim 9, characterized in that, The limiting oxygen index of the flame-retardant polyester is greater than 22.

16. The flame-retardant polyester according to claim 15, characterized in that, The limiting oxygen index of the flame-retardant polyester is greater than 24.

17. The flame-retardant polyester according to claim 16, characterized in that, The limiting oxygen index of the flame-retardant polyester is not less than 27.

18. A method for preparing flame-retardant polyester according to any one of claims 9 to 17, characterized in that, Before melt blending ethylene terephthalate and a multi-element integrated flame retardant containing a Schiff base structure, the PET is first quenched and pulverized.

19. The preparation method according to claim 18, characterized in that, The melt blending temperature is 240-280℃.

20. The preparation method according to claim 19, characterized in that, The melt blending temperature is 260-270℃.

Images