Synthesis method of a new phytic acid flame retardant and its products and applications

Abstract

The present invention discloses a synthesis method of a novel phytic acid flame retardant, its product and application. The present invention has found that polyvinyl phytic acid (PPVA) and glutaraldehyde can be grafted onto cotton fabric through a three-dimensional network structure, and greatly improves the flame retardant performance of the cotton fabric, with the limiting oxygen index reaching 60.1%.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant preparation, and particularly relates to a synthesis method of a novel phytic acid flame retardant, a product thereof and an application thereof. Background Art

[0002] Thanks to the rapid advancement of science and technology in the textile industry, the research, development, and application of textile products have unprecedented potential. Cotton fabrics, with their high mechanical strength and pleasant hand feel, are widely recognized as a natural fiber with excellent comfort, breathability, and moisture absorption, enjoying widespread application prospects in today's society. However, cotton textiles have a high heat release rate, rapid flame spread, and are easily flammable. Their limiting oxygen index (LOI) is only around 18%, far below the standard for flame-retardant fibers, seriously impacting property and lives. Consequently, the public is paying close attention to flame-retardant finishing of cotton fibers. The expanding application of fire-resistant materials is placing higher demands on the fire resistance of cotton fabrics. Phosphorus-based flame retardants are attracting widespread attention for their flame-retardant and environmentally friendly properties. These flame retardants generate phosphoric acid or phosphoric anhydride during combustion, dehydrating and carbonizing flammable materials, thereby preventing or reducing the generation of flammable gases. They can be divided into two categories based on the elements they contain: inorganic and organic. Organophosphorus-based flame retardants, including phosphates, phosphites, and phosphonates, are the most widely used. When phosphorus-based flame retardants are pyrolyzed, phosphoric anhydride decomposes to form a melt with a structure similar to the combustible surface of glass. Upon oxidation, it produces carbon dioxide, which acts as a flame retardant. Organophosphorus flame retardants are more diverse than other flame retardants and offer advantages such as high efficiency and non-toxicity. They are recognized as a suitable alternative to halogenated flame retardants that meet the fire protection requirements of textiles, satisfying modern demands for flame-retardant finishes on textiles. Biomass flame retardants are considered an excellent alternative to traditional flame retardants due to their environmental safety, strong renewable capacity, and abundant sources. Given the current environment, the development of pollution-free, safe, stable, and highly effective biomass flame retardant materials is of vital importance to the textile industry. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and to briefly introduce some preferred embodiments.

[0004] As one aspect of the present invention, the present invention provides a method for synthesizing a novel phytic acid flame retardant, which comprises the following steps:

[0005] Dicyandiamide, urea and polyvinyl alcohol are weighed and dissolved in dimethyl sulfoxide. Nitrogen is used as a protective gas for the reaction, and the mixture is stirred and heated. A phytic acid solution is added to carry out a reaction. After the reaction is completed, the mixture is filtered. The filtered solution is added dropwise into anhydrous ethanol, and the mixture is centrifuged. The resulting solid is collected and dried to obtain polyvinyl phytate.

[0006] As a preferred embodiment of the synthesis method of the novel phytic acid flame retardant of the present invention, the method of weighing dicyandiamide, urea and polyvinyl alcohol and dissolving them in dimethyl sulfoxide is as follows: 2 g of dicyandiamide, 5 g of urea and 0.8 g of polyvinyl alcohol are weighed and dissolved in 100 mL of dimethyl sulfoxide.

[0007] As a preferred solution of the synthesis method of the novel phytic acid flame retardant of the present invention: the stirring and heating is stirring and heating to 100°C.

[0008] As a preferred embodiment of the synthesis method of the novel phytic acid flame retardant of the present invention, the step of adding the phytic acid solution to carry out the reaction comprises adding 14 mL of the phytic acid solution and reacting at 110° C. for 2 hours.

[0009] As another aspect of the present invention, the present invention provides an application of the novel phytic acid flame retardant in flame retardant finishing of cotton fabrics, wherein: the polyvinyl phytate is added to a glutaraldehyde aqueous solution to prepare a polyvinyl phytate flame retardant finishing liquid, the cotton fabric is placed in the liquid after heating, double-dipped and double-rolled, and dried to obtain the flame-retardant finished cotton fabric.

[0010] As a preferred solution for the application of the novel phytic acid flame retardant of the present invention in flame retardant finishing of cotton fabrics: the polyvinyl phytate is added to a glutaraldehyde aqueous solution to prepare a polyvinyl phytate flame retardant finishing solution, wherein the concentration of the glutaraldehyde aqueous solution is 8-10 wt%.

[0011] As a preferred solution for the application of the novel phytic acid flame retardant of the present invention in flame retardant finishing of cotton fabrics: the polyvinyl phytate is added to a glutaraldehyde aqueous solution to prepare a polyvinyl phytate flame retardant finishing liquid, wherein the concentration of the polyvinyl phytate in the polyvinyl phytate flame retardant finishing liquid is 200-400 g / L.

[0012] As a preferred solution for the application of the novel phytic acid flame retardant of the present invention in flame retardant finishing of cotton fabrics, the cotton fabric is placed therein after heating to 40° C., and the bath ratio of the cotton fabric is 1:80.

[0013] As a preferred solution for the application of the novel phytic acid flame retardant of the present invention in flame retardant finishing of cotton fabrics: the drying is performed by pre-drying at 90°C for 3 minutes and then baking at 160°C for 3 minutes using a heat setting machine.

[0014] Beneficial effects of the present invention: Polyvinyl alcohol phytic acid (PPVA) is synthesized using polyvinyl alcohol (PVA) and phytic acid (PA), a natural polyhydroxy compound containing phosphate groups, as raw materials, dimethyl sulfoxide (DMSO) as a solvent, dicyandiamide as a dehydrating agent, and urea as a catalyst. PPVA is then grafted onto cotton fabric using a glutaraldehyde cross-linking method. Characterization of the PPVA-treated cotton fabric using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) revealed successful grafting of PPVA onto the cotton fabric. The thermal properties of the treated cotton fabric were also studied using thermogravimetric analysis, limited oxygen index, and vertical combustion tests. The initial degradation temperature and maximum cracking temperature of the treated cotton fabric are earlier than those of the original cotton fabric, the exothermic peak area is greatly reduced, and the remaining residue at 590°C is 45.3%, which is 41.35% higher than that of the original cotton fabric; the cotton fabric treated with 400g / L PPVA finishing agent has a limiting oxygen index of 60.1%, which is much higher than the 17.5% of the untreated cotton fabric; the vertical burning test found that the cotton fabric samples treated with PPVA have a high ignition point, are difficult to ignite, and have excellent self-extinguishing ability, with no afterflaming or smoldering time.

[0015] The present invention has found that polyvinyl alcohol phytic acid (PPVA) and glutaraldehyde can be grafted onto cotton fabric through a three-dimensional network structure, and greatly improve the flame retardant properties of cotton fabric, with a limited oxygen index of 60.1%, much higher than that of phytic acid (PA) finishing cotton fabric, wherein the role of glutaraldehyde is very critical, glutaraldehyde greatly improves the crosslinking efficiency of phytic acid (PA) on cotton fabric, and the grafting reaction between the flame retardant PPVA and the cotton fabric not only occurs on the fiber surface, but also enters the fiber interior to react, significantly improving the crosslinking fastness, and then significantly improving the limited oxygen index. The finishing agent of the present invention is very significant for the flame retardant finishing of cotton fabric, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments, wherein:

[0017] Figure 1 This is the synthetic route of PPVA.

[0018] Figure 2 This is the synthesis process of PPVA.

[0019] Figure 3 It is the finishing liquid after the reaction.

[0020] Figure 4 It is an infrared spectrum.

[0021] Figure 5 This is the XPS analysis diagram.

[0022] Figure 6 This is a scanning electron microscope image of the fabric and its combustion residue.

[0023] Figure 7 This is energy spectrum analysis after combustion.

[0024] Figure 8 TG and DTG diagrams of OCF and PCF. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0026] Example 1:

[0027] 100 mL of dimethyl sulfoxide (DMSO) was used as the reaction solvent and added to a three-necked flask. 2 g of dicyandiamide, 5 g of urea, and 0.8 g of polyvinyl alcohol (0588 type) were weighed and added to the three-necked flask in sequence. They were dissolved in the solvent DMSO in sequence. Nitrogen was used as the protective gas for the reaction. The mixture was stirred and heated to 100°C. After the raw materials were completely dissolved, 14 mL of phytic acid solution was added to the flask and reacted at 110°C for 2 hours. The obtained product was filtered to remove the precipitate, and the obtained solution was then added dropwise to anhydrous ethanol. The crystal solution was then centrifuged to separate the crystals. A solid was then obtained. The obtained solid was dissolved in deionized water and then added to anhydrous ethanol for recrystallization. The final solid was dried in a freeze dryer to obtain a polyvinyl phytate (PPVA) solid product.

[0028] Flame retardant cotton fabric finishing:

[0029] Scheme 1: First prepare a 10wt% glutaraldehyde aqueous solution, add a certain amount of the polyvinyl phytate (PPVA) to the 10vol% glutaraldehyde aqueous solution to prepare polyvinyl phytate (PPVA) flame retardant finishing liquids with concentrations of 400g / L, 300g / L, and 200g / L, respectively. Then, according to a cotton fabric bath ratio of 1:80, heat the polyvinyl phytate (PPVA) flame retardant finishing liquid to 40°C and place the cotton fabric therein. After magnetic stirring for 30 minutes, take out and dip and pad once, stir for another 30 minutes, take out and dip and pad twice, after rolling dry, pre-bake at 90°C for 3 minutes, and then bake at 160°C for 3 minutes in a heat setting machine to obtain the flame-retardant finished cotton fabric.

[0030] Solution 2: Prepare PPVA aqueous solutions with concentrations of 400g / L, 300g / L, and 200g / L respectively, and place the fabric in them at room temperature according to a bath ratio of 1:80. Then, raise the temperature to 40°C, add glutaraldehyde to prepare a glutaraldehyde solution with a mass concentration of 10wt%. After stirring with magnetic stirring for 30 minutes, take out and dip once, stir for another 30 minutes, take out and dip and pad twice, after rolling dry, pre-bake at 90°C for 3 minutes, and then bake at 160°C for 3 minutes in a heat setting machine.

[0031] Determination of the finishing scheme: Glutaraldehyde and PPVA finishing agents may produce aldol reaction and thus cross-link. In Scheme 2, the temperature is raised to 40°C and then glutaraldehyde solution is added. The glutaraldehyde therein directly cross-links with PPVA, resulting in unsatisfactory finishing of flame-retardant cotton fabric. Therefore, Scheme 1 was determined as the finishing scheme.

[0032] like Figure 1 As shown in the figure, dimethyl sulfoxide (DMSO) was used as the solvent for this reaction, and urea and dicyandiamide acted as dehydration catalysts in the esterification reaction. Urea can accelerate the dehydration of H + The water contained in the phytic acid solution can hydrolyze the urea molecules, while dicyandiamide can prevent the hydrolysis of urea, making the urea -NH4 + exists in the form of NH3, rather than being hydrolyzed and released. + It can induce polarization of the ortho-hydroxyl groups of phytic acid, thereby promoting esterification and increasing the esterification rate, and finally obtaining more polyvinyl phytate (PPVA). During the synthesis process, the hydroxyl groups in the phytic acid molecules are polarized by the urea molecules and react with the hydroxyl groups of PVA to form -NH4 + Form removal. Figure 1 This is the synthetic route of PPVA. Figure 2 This is the synthesis process of PPVA. Figure 3 It is the finishing liquid after the reaction.

[0033] Test method:

[0034] Infrared spectroscopy (FT-IR):

[0035] Because the chemical structures of compounds vary greatly, they cannot be intuitively detected and judged. However, different functional groups have different absorption in different infrared light regions, and therefore absorption peaks appear in different infrared light spectra. Therefore, infrared spectroscopy can be used to provide a reference for the qualitative identification of compounds. Cotton fabrics before and after PPVA treatment were measured, and the scanning range was set to 600-4000cm -1 .

[0036] X-ray Photoelectron Spectroscopy (XPS):

[0037] The PPVA sample was scanned on an X-ray photoelectron spectrometer, and high-resolution spectra of each element were obtained after peak fitting. The composition and structure of the sample were studied by analyzing the energy of photoelectrons emitted by each element in the sample.

[0038] Scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS):

[0039] Scanning electron microscopes (SEMs) possess powerful microscopic imaging capabilities, making it easy to observe magnified fabric surface morphology. During measurements, the SEM's accelerating voltage was set to 5.00 kV. Samples were mounted on a copper sheet and observed at different magnifications before and after finishing, as well as before and after burning. Quantitative elemental analysis of the samples was performed using an energy dispersive X-ray analyzer.

[0040] Combustion performance of cotton fabrics:

[0041] Among the many flame retardant testing methods for cotton fabrics, the vertical burning test and the limiting oxygen index test are the most important. The limiting oxygen index is determined according to GB / T 5454-1997, using a 150mm x 58mm specimen. The minimum oxygen content required to sustain combustion is measured, which is the measured LOI value. The vertical burning test is also conducted according to GB / T 5455-1997, and the damaged length, smoldering time, and afterflame time are recorded.

[0042] Thermal stability of cotton fabrics:

[0043] Thermogravimetric analysis mainly consists of three parts: temperature control system, mass temperature time recording system, and detection query system. Based on the characteristic that the mass of substances changes with temperature and time, their properties are studied. The thermogravimetric analyzer was used to test PPVA-treated cotton fabrics under nitrogen to analyze their thermal stability. The test temperature range was 20-800°C.

[0044] Mechanical properties of cotton fabrics:

[0045] The tensile strength and elongation at break of cotton fabrics before and after finishing were tested according to GB / T 3917-2009. The fabric size was 5 cm × 15 cm.

[0046] Experimental results:

[0047] FT-IR spectrum analysis: 1300~1100cm -1 Within this range, esters will have absorption peaks, which is due to the stretching vibration of CO, but CO will change due to the different groups it is connected to. This is an important basis for determining ester compounds by infrared spectroscopy. Figure 4 (a) is the infrared spectrum of PPVA, 3196 cm -1The absorption peak at 1044 cm corresponds to the stretching vibration of -OH in the PPVA molecule. -1 The strong and sharp characteristic absorption peak near 1153cm is due to the presence of POC bond. -1 The characteristic absorption peak at 1701 cm is attributed to the stretching vibration of the ester CO bond. -1 The absorption peak at , which is due to the presence of -P=O-. According to the presence of the characteristic absorption peaks of -P=O- and POC bonds, it is proved that the esterification reaction has indeed occurred. The above characteristic peaks are consistent with the target product. The infrared spectra of PPVA treated cotton fabric (PCF) and original cotton fabric (OCF) are shown in Figure 2. Figure 4 (b), OCF at 3341 cm -1 There is an absorption peak at 2904cm, which is due to the presence of -OH bonds in cellulose fibers. -1 The absorption peak at 1107cm is due to the stretching of -CH bond. -1 There is also an absorption peak at 1701cm, which is due to the stretching vibration of the COC bond in the cellulose macromolecule. Compared with OCF, the infrared spectrum of PCF shows some new changes. -1 The absorption peak at 1158cm is caused by the vibration of P=O, while the absorption peak at 1158cm -1 The absorption peak at 1054 cm is caused by the stretching vibration of the CO bond in the ester molecule, while the absorption peak at 1054 cm -1 The strong absorption peaks at the wavenumbers are caused by the stretching vibration of the POC bond. These indicate that the synthesized PPVA finishing agent was successfully grafted onto the cotton fabric through the cross-linking effect of glutaraldehyde.

[0048] XPS spectrum analysis: XPS test analysis was performed on PCF and OCF samples to further determine the composition structure of PPVA. Figure 5 (a) shows the full spectrum of PCF and OCF. The OCF mainly shows the elements C (C1s, 286.25eV, atomic percentage 63.45%) and O (O1s, 532.75eV, atomic percentage 36.55%). In addition to C (C1s, 286.59eV, atomic percentage 34.76%) and O (O1s, 525.54eV, atomic percentage 43.64%), the flame retardant element P (P2p, 124.54eV, atomic percentage 9%) can also be observed in the PCF spectrum. As expected, the characteristic of the cotton fabric modification reaction in this experiment is the introduction of the flame retardant element P. Figure 5 (b) shows the C1s high-resolution spectrum of OCF, in which absorption peaks appear at 288.0 eV, 286.6 eV, and 284.85 eV. These three peaks are caused by OCO, CO, and CH / CC in cellulose molecules. Figure 5(c), (d) and (e) show the high-resolution spectra of C1s, O1s and P2p of PCF. In the C1s spectrum, the strong absorption peaks at 284.7eV and 286.6eV are due to CC / CH and CO. In the O1s spectrum, the strong absorption peak at 531.2eV corresponds to P=O, while the strong absorption peak at 532.8eV is due to CO. In the P2p spectrum, the strong absorption peak at 133.6eV is due to the presence of P=O bonds, and the strong absorption peak at 134.3eV is due to POC / PO3 2- According to the XPS spectrum analysis results, the above results are consistent with other research results, indicating that PPVA containing phosphate has been successfully introduced into cotton fabrics.

[0049] Scanning electron microscopy (SEM) analysis: The SEM images of the fabric samples and the residues after burning showed Figure 6 . Figure 6 (a) and Figure 6 (c) shows the electron microscope images of OCF before and after combustion. It can be clearly seen from the image that the fabric fibers have a smooth surface, clear texture and are flat ribbon-like. The OCF after combustion also has structural fibers that are twisted in opposite directions along the length. Figure 6 (b) and Figure 6 (d) is a scanning electron microscope image of PCF before and after combustion. The surface of the treated cotton fabric becomes rougher, and the active ingredients are fixed on the cotton fibers. Each fiber is evenly coated with a layer of active ingredients. This shows that the grafting reaction between the flame retardant PPVA and the cotton fabric not only occurs on the fiber surface, but also enters the fiber interior to react. Figure 6 (c) and Figure 6 (d) It can be found that PCF shows a denser and more continuous carbon layer. The dense carbon layer protects the cotton fabric from the damage of flames and active small molecules, and can effectively inhibit the transfer of heat and substances to achieve an ideal flame retardant effect. It can also be found in the figure that the carbon frame of the cotton fabric remains basically intact without cracks after combustion, and its fiber surface is rough, such as Figure 6 As shown in the figure, OCF shrinks after combustion, while PCF can still maintain its complete carbon structure shape after combustion.

[0050] Energy dispersive spectrometry (EDS) analysis: In order to study the element content of the sample after combustion, the residue was collected and subjected to energy dispersive spectrometry analysis. Figure 7As shown, the OCF residue appears loose and thin, indicating that the main structure has been severely damaged by the flames. In contrast, the PCF sample retains a relatively intact original fabric shape after combustion. Only carbon and oxygen are detectable in the OCF, while phosphorus is also detected in the PCF. This phosphorus originates from the finishing agent, further demonstrating that the flame retardant component has been successfully grafted onto the cotton fabric. The finished cotton fabric still contains 18.04% phosphorus after combustion, indicating that the PCF sample retains its flame retardant properties.

[0051] Thermal stability analysis: The thermal stability of flame retardant cotton fabrics was measured in a nitrogen environment using a thermogravimetric analyzer. Figure 8 As can be seen, within the OCF temperature range of 301.5°C, the sample begins to lose moisture, reducing its mass by 7.2%. Within the 301.5°C-371.55°C range, the fabric's mass loss rapidly accelerates, reaching a maximum rate of loss at 352.62°C. Within this temperature range, cellulose macromolecules rapidly cleave, producing large soot particles, resulting in a 66.44% mass loss. After reaching 371.55°C, the mass loss slows, and at 479.82°C, a 3.95% mass residue remains. Compared to the OCF sample, the PCF's initial degradation temperature is 262.40°C, earlier than that of the OCF. This earlier degradation temperature may be due to the grafted flame retardant, which releases its active ingredients first, inhibiting flame retardancy. This conclusion is further confirmed by the PCF's residual rate at 590°C: the PCF's residual rate is 45.3%, 41.35% higher than that of the OCF. Compared to OCF, the onset and maximum degradation temperatures of PCF also shift earlier due to the earlier decomposition of the flame retardant. To better understand the thermal decomposition phenomenon, the DTG values ​​of OCF and PCF were further investigated under a nitrogen atmosphere. It is also clear that PCF thermally decomposes earlier than OCF, and the peak intensity of the former is much less than that of the latter. However, the PCF curve lacks distinct peak separation, and its exothermic peak area is significantly reduced, indicating a strong bond between PPVA and cotton cellulose. This early decomposition successfully releases sufficient active substances to exert the flame retardant effect. For example, the highly acidic phosphate esters in PVA promote significant fiber dehydration, thereby increasing char formation. The char layer impedes oxygen penetration into the fiber, protecting the underlying fibers from high-temperature damage. The water released during char formation acts to dilute oxygen and dissipate heat. These data demonstrate that cotton fabrics treated with PPVA can achieve excellent thermal stability and demonstrate the feasibility of this flame-retardant finish.

[0052] Analysis of flame retardant properties of cotton fabrics Under the condition of controlling other factors unchanged, the concentration of flame retardant finishing agent was changed to 200g / L, 300g / L, and 400g / L, and the cotton fabrics treated with these finishing agents were tested and characterized. The results are shown in Table 1.

[0053] Untreated raw cotton fabric is highly flammable, with a LOI of only 17.5%, far below the flame retardant standard of 26-28%, as shown in Table 1. The flame retardancy of treated cotton fabrics significantly improves with increasing flame retardant concentration, with weight gain, LOI, and flame retardant efficacy all increasing accordingly. At a flame retardant concentration of 200 g / L, the fabric's weight gain reached 28.9% and LOI reached 40.6%. Both the smoldering time and afterflame time were zero, demonstrating excellent self-extinguishing properties. The fabric's damage length was 80 mm, demonstrating excellent flame retardancy. At a flame retardant concentration of 300 g / L, the LOI reached 49.9% and the weight gain was 31.9%. At 400 g / L, the weight gain reached 39.2%, the LOI as high as 60.1%, and there was no smoldering or afterflame time, with a damage length of only 55 mm, demonstrating excellent flame retardancy. This is attributed to the fact that under high temperature conditions, the PPVA flame retardant molecules will decompose into molecules such as phosphoric acid, thereby increasing the carbonization rate of cellulose molecules and forming a continuous carbon layer to achieve condensed phase flame retardancy, thereby achieving the purpose of improving the flame retardancy of cotton fabrics.

[0054] Table 1 Vertical combustion test and limiting oxygen index test results

[0055]

[0056]

[0057] Figure 4 Infrared spectra of PPVA (a) and cotton fabric before and after treatment (b). Figure 5 XPS analysis of (a) overall spectrum of OCF and PCF, (b) C1s of OCF, (c) C1s of PCF, (d) O1s of PCF, and (e) P2p of PCF. Figure 6 Scanning electron micrographs of the fabric and its combustion residues. (a) and (c) are scanning electron micrographs of the fabric before and after OCF combustion; (b) and (d) are scanning electron micrographs of the fabric before and after PCF combustion; (e) is a photograph of the ash after combustion of the raw cotton fabric; and (f) is a photograph of the carbon layer formed after combustion of the finished fabric. Figure 7 Energy spectrum analysis of OCF and PCF after combustion. Figure 8 (a) TG and (b) DTG diagrams of OCF and PCF.

[0058] This invention synthesizes polyvinyl phytic acid (PPVA) using polyvinyl alcohol (PVA) and phytic acid (PA), a natural polyol containing phosphate groups, as raw materials, dimethyl sulfoxide (DMSO) as a solvent, dicyandiamide as a dehydrating agent, and urea as a catalyst. PPVA is then grafted onto cotton fabric using a glutaraldehyde cross-linking method. Characterization of the PPVA-treated cotton fabric using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) revealed successful grafting of PPVA onto the cotton fabric. The thermal properties of the treated cotton fabric were also investigated using thermogravimetric analysis, limited oxygen index, and vertical combustion tests. The initial degradation temperature and maximum cracking temperature of the treated cotton fabric are earlier than those of the original cotton fabric, the exothermic peak area is greatly reduced, and the remaining residue at 590°C is 45.3%, which is 41.35% higher than that of the original cotton fabric; the cotton fabric treated with 400g / L PPVA finishing agent has a limiting oxygen index of 60.1%, which is much higher than the 17.5% of the untreated cotton fabric; the vertical burning test found that the cotton fabric samples treated with PPVA have a high ignition point, are difficult to ignite, and have excellent self-extinguishing ability, with no afterflaming or smoldering time.

[0059] The present invention has found that polyvinyl alcohol phytic acid (PPVA) and glutaraldehyde can be grafted onto cotton fabric through a three-dimensional network structure, and greatly improve the flame retardant properties of cotton fabric, with a limited oxygen index of 60.1%, much higher than that of phytic acid (PA) finishing cotton fabric, wherein the role of glutaraldehyde is very critical, glutaraldehyde greatly improves the crosslinking efficiency of phytic acid (PA) on cotton fabric, and the grafting reaction between the flame retardant PPVA and the cotton fabric not only occurs on the fiber surface, but also enters the fiber interior to react, significantly improving the crosslinking fastness, and then significantly improving the limited oxygen index. The finishing agent of the present invention is very significant for the flame retardant finishing of cotton fabric, and has good industrial application prospects.

[0060] In the prior art, due to the low direct reaction ability of cellulose with phytic acid, the effect of subsequent flame retardant finishing will be affected, resulting in a low limiting oxygen index. The present invention has found that the LOI is significantly improved after adopting the method of the present invention. The reason for this phenomenon may be that PVA has a strong reaction ability with phytic acid, which can better graft more phytic acid onto the macromolecular chain. The grafted PPVA macromolecules penetrate into the amorphous area of ​​cellulose and form an interpenetrating network structure with the cellulose macromolecular chain. The flame retardant finishing environment can also loosen some crystalline areas, allowing PPVA to enter to a certain extent. In addition, the large number of phosphorus hydroxyl groups, alcohol hydroxyl groups and the large number of hydroxyl groups on cellulose possessed by PPVA can form a complex three-dimensional hydrogen bond network structure, which on the one hand strengthens the fixation of the grid. On the other hand, even if some hydrogen bonds are destroyed during use, new hydrogen bonds can be quickly formed at new positions. These processes enhance the retention ability of PPVA in cotton fibers. At the same time, the present invention forms a strong covalent chemical crosslink between PPVA and cellulose macromolecular chains through glutaraldehyde treatment. On the one hand, glutaraldehyde can form a chemical bridge between PPVA and fiber macromolecules through acetal reaction. On the other hand, it also has a certain degree of crosslinking effect between cellulose macromolecules, thereby forming a clamping effect on the microstructure, locking a large amount of PPVA in cellulose, and synergistically improving the flame retardant performance.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. Application of a novel phytic acid flame retardant in flame retardant finishing of cotton fabrics, characterized in that: The synthesis method of the novel phytic acid flame retardant comprises the following steps: weighing dicyandiamide, urea and polyvinyl alcohol, dissolving them in dimethyl sulfoxide, using nitrogen as a protective gas for the reaction, stirring and heating, adding a phytic acid solution, reacting, filtering after the reaction, adding the filtered solution dropwise into anhydrous ethanol, centrifuging, collecting the resulting solid, and drying to obtain polyvinyl alcohol phytate; The polyvinyl phytate is added to a glutaraldehyde aqueous solution to prepare a polyvinyl phytate flame retardant finishing solution, and the cotton fabric is placed in the solution after heating to 40° C., with a bath ratio of 1:80; the cotton fabric is subjected to two dipping and two padding, and then dried to obtain a flame retardant finished cotton fabric; wherein the concentration of the glutaraldehyde aqueous solution is 10 wt %; and the concentration of the polyvinyl phytate in the polyvinyl phytate flame retardant finishing solution is 400 g / L; The drying process is to pre-dry at 90° C. for 3 minutes and then bake at 160° C. for 3 minutes using a heat setting machine.

2. The use according to claim 1, wherein: The weighing of dicyandiamide, urea and polyvinyl alcohol and dissolving them in dimethyl sulfoxide is as follows: 2 g of dicyandiamide, 5 g of urea and 0.8 g of polyvinyl alcohol are weighed and dissolved in 100 mL of dimethyl sulfoxide.

3. The use according to claim 1 or 2, characterized in that: The stirring and heating is stirring and heating to 100°C.

4. The use according to claim 2, wherein: The adding of phytic acid solution to carry out reaction is to add 14 mL of phytic acid solution and react at 110° C. for 2 hours.

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