A finishing flame retardant and its preparation method and application

Abstract

The application provides a finishing flame retardant and a preparation method and application thereof, and belongs to the technical field of functional textiles. The molar ratio of trialkyl phosphite and ethanolamine is 1:1.5-1:2.5, the reaction temperature of the ester exchange reaction is 80-180 DEG C, the reaction time is 4-18 hours, then unreacted trimethyl phosphite is removed by distillation, and the phosphite ester flame retardant is obtained, which is a mixture, the preparation method only needs one-step reaction, does not need to add an organic solvent, and does not need to collect tail gas, and the preparation process is simple, green and environment-friendly. The application provides a flame-retardant and anti-melt-dripping polyester fabric, polyols are introduced as carbon sources to further compound with the phosphite ester flame retardant, the phosphite ester can change the decomposition path of the polyester fabric at high temperature and promote the dehydration of the polyols into carbon, the two components produce a synergistic effect to form a protective layer covering the surface of the polyester fabric to inhibit the melt dripping and falling, and the nitrogen source is compounded to simultaneously play the condensed phase flame-retardant mechanism and the gas phase flame-retardant mechanism.

Description

Technical Field

[0001] This invention relates to the field of textile finishing technology, and in particular to a finishing flame retardant, its preparation method, and its application. Background Technology

[0002] Textiles are used in all aspects of our daily lives; however, as a type of polymer material, most textiles are flammable. Polyester is currently the world's most produced and widely used synthetic fiber, possessing many advantages such as high abrasion resistance and good wrinkle resistance, and is widely used in clothing manufacturing, decorative products, and other fields. However, polyester is easily ignited when exposed to flames, and during combustion, it releases a large amount of heat and flaming drips, causing rapid spread of fire and secondary burns to people or animals, posing a great threat to people's lives and property. Therefore, flame-retardant and anti-dripping treatment of polyester is of great significance.

[0003] Currently, flame retardants are mainly classified into phosphorus-based, nitrogen-based, silicon-based, and boron-based flame retardants. Among them, phosphorus-based flame retardants occupy an important position in the field of fabric flame retardant modification due to their excellent flame retardant effect, low smoke and low toxicity. In addition, compounding different flame retardants can enable synergistic effects between the components, and simultaneously exert the flame retardant mechanism of condensed phase and gas phase, thereby improving flame retardant efficiency.

[0004] Currently, flame retardants used in polyester fabrics are mainly organic phosphite or phosphate flame retardants, which have high flame retardant efficiency. However, most of these flame retardants are synthesized by phosphorus-containing acyl chlorides or acid anhydrides, which require the addition of organic solvents and strict control of reaction conditions. In addition, the reaction produces acid gas, which needs to be collected, resulting in high environmental pressure, high corrosiveness to equipment, and high acid value of the finished product, thus limiting its application. For example, in invention patent CN 114031640A, a phosphate ester type flame retardant is synthesized through a three-step reaction using chloropropanediol, phosphorus trichloride, phenol, formaldehyde, and epichlorohydrin as raw materials. Phosphorus trichloride and formaldehyde are used, which are highly dangerous and produce a large amount of hydrochloric acid gas as a byproduct. In addition, this method has too many reaction steps and low synthesis efficiency. The anti-dripping effect of polyester fabric is mainly achieved by forming a protective carbon layer through the action of condensed phase. However, the current preparation method of flame-retardant and anti-dripping polyester fabric faces the problem of many steps and cumbersome process. For example, patent CN 111188193B discloses a flame-retardant and anti-dripping polyester fabric and its preparation method. The polyester fabric after flame-retardant treatment can effectively retard flame and resist dripping. However, the preparation method adopts a layer-by-layer self-assembly method, which requires repeated deposition of anionic and cationic layers, and the number of anionic and cationic layers is more than 3, making the preparation process cumbersome. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned shortcomings of the prior art by providing a finishing flame retardant, its preparation method, and its application, thereby solving the technical problems of harsh synthesis conditions, environmental unfriendliness, and complex finishing processes for flame-retardant fabrics associated with traditional flame retardants.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a method for preparing a finishing flame retardant, comprising: subjecting a trialkyl phosphite and ethanolamine to an ester exchange reaction at a molar ratio of 1:1.5 to 1:2.5; reacting at a temperature of 80°C to 180°C for 4 to 18 hours; and then distilling to remove unreacted trimethyl phosphite to obtain the finishing flame retardant, namely, a phosphite flame retardant. The finishing flame retardant is a mixture, and its general compound formula is shown in Formula I. Equation I, where n is 0, 1, and 2.

[0007] A second objective of this invention is to provide a finishing flame retardant prepared using the above-described preparation method.

[0008] A third objective of this invention is to provide the application of the above-mentioned finishing flame retardant in the preparation of flame-retardant and anti-drip polyester fabrics.

[0009] A fourth objective of this invention is to provide a finishing liquid comprising the aforementioned compound and a polyol.

[0010] The fifth objective of this invention is to provide a method for preparing flame-retardant and anti-drip polyester fabric, comprising the following specific steps: S1. Phosphite flame retardant was prepared using the above preparation method; S2. The phosphite flame retardant obtained in S1 is mixed with a polyol to obtain a composite flame retardant. The composite flame retardant is dissolved in water and stirred evenly to obtain a finishing solution. The polyol is pentaerythritol or glycerol. S3. Pre-treat the surface of the polyester fabric; S4. The pretreated polyester fabric is immersed in the finishing solution described in S2, and after drying, a flame-retardant and anti-drip polyester fabric is obtained. Furthermore, the molar ratio of the trialkyl phosphite to ethanolamine is 1:1.5 to 1:2.5.

[0011] Furthermore, the transesterification reaction is carried out at a temperature of 80℃-180℃ and for a time of 4h-18h.

[0012] Furthermore, the mass concentration of the phosphite flame retardant in the finishing solution is 5% to 40%, and the mass concentration of the polyol is 4% to 15%.

[0013] Furthermore, the alkaline solution is a sodium hydroxide solution or a sodium carbonate solution; the concentration of the alkaline solution is 1 mol / L to 1.5 mol / L.

[0014] Furthermore, the impregnation treatment time is 2-6 hours; the bath ratio is 1:10-1:20. The drying treatment temperature is 60℃-100℃; the time is 10-30 minutes.

[0015] The fourth objective of this invention is to provide a flame-retardant and anti-drip polyester fabric obtained by the above-described preparation method.

[0016] Furthermore, the limiting oxygen index of the flame-retardant and anti-dripping polyester fabric is 25.7%~28.8%, and the damaged length is 4.1cm~9.3cm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention provides a finishing flame retardant, which is synthesized by transesterification of trialkyl phosphite and ethanolamine, and is a mixture. Its general compound formula is shown in Formula I. Formula I, where n is 0, 1, and 2. This method avoids the use of phosphorus trichloride, a traditional reagent for the synthesis of phosphites. Ethanolamine serves as both a reactant and a catalyst, and the reaction requires only one step, eliminating the need for organic solvents and tail gas collection. The preparation process is simple, green, and environmentally friendly.

[0018] (2) The phosphite flame retardant provided by the present invention contains multiple active groups, which is beneficial for further modification and has strong structural designability.

[0019] (3) The present invention provides a flame-retardant and anti-dripping polyester fabric, which introduces polyol as a carbon source and further combines it with phosphite flame retardant. Phosphite can change the decomposition path of polyester fabric at high temperature and promote the dehydration of polyol into carbon. The two components produce a synergistic effect to form a protective layer covering the surface of polyester fabric to inhibit dripping. It also combines nitrogen source to exert both condensed phase flame retardant mechanism and gas phase flame retardant mechanism.

[0020] (4) The method for preparing a flame-retardant and anti-drip polyester fabric provided by the present invention is simple, has low preparation cost, is green and environmentally friendly, and is easy to scale up. Attached Figure Description

[0021] Figure 1 Fourier transform infrared spectra of flame-retardant and anti-drip polyester fabric and pure polyester fabric provided in Example 3; Figure 2 The images show SEM images of pure polyester fabric before and after combustion. In the image, (a) is before combustion; and (d) is after combustion. Figure 3 The images show SEM images of the flame-retardant and anti-dripping polyester fabric prepared in Example 3 before and after combustion. In the images, (b) is before combustion and (c) is after combustion. Figure 4The images show SEM images of the flame-retardant and anti-dripping polyester fabric prepared in Example 5 before and after combustion. In the images, (e) is before combustion and (f) is after combustion. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] All reagents used in this invention are commercially available.

[0024] The post-treatment flame retardant provided by this invention includes compounds as shown in Formula I. Formula I, where n is 0, 1, or 2. A transesterification reaction is carried out at a molar ratio of 1:1.5 to 1:2.5 between trialkyl phosphite and ethanolamine, at a reaction temperature of 80℃ to 180℃, for a reaction time of 4h to 18h. Unreacted trimethyl phosphite is then removed by distillation to obtain the phosphite flame retardant.

[0025] In this invention, the mass concentration of the phosphite flame retardant in the finishing solution is 5%~40%, and the mass concentration of the polyol is 4%~15%. Increasing the amount of phosphite flame retardant helps to improve the flame retardant properties of polyester fabrics, but if the amount is too high, it will result in an excessive load on the fabric, thus affecting the fabric's hand feel. If the amount of polyol is too low, the prepared flame-retardant polyester fabric will have poor anti-dripping effect, while if the amount is too high, it will not be completely dissolved in water or will reduce the flame retardant properties.

[0026] Example 1 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0027] The specific steps are as follows: Step S1: Add 0.1 mol of trimethyl phosphite and 0.2 mol of ethanolamine to a three-necked flask, heat to 100°C and react for 4 hours. Remove unreacted trimethyl phosphite by distillation to obtain a phosphite flame retardant. This phosphite flame retardant is a mixture, and its general compound formula is shown in Formula I. Equation I, where n is 0, 1, and 2.

[0028] Step S2: Dissolve the phosphite flame retardant and pentaerythritol in water to obtain a mixed solution. The mass concentration of the phosphite flame retardant in the finishing solution is 5%, and the mass concentration of the pentaerythritol is 6%.

[0029] Step S3: Pre-treat the polyester fabric to swell the fibers and reduce impurities on the fabric.

[0030] Prepare a 1 mol / L NaOH solution, immerse the polyester fabric in the solution for 24 hours, then rinse it repeatedly with deionized water until the surface of the polyester fabric is nearly neutral, and dry it at 80℃ for later use.

[0031] Step S4: Immerse the pretreated polyester fabric in the finishing solution at a ratio of 1:20. After 6 hours, dry the polyester fabric at 80°C for 20 minutes to obtain a flame-retardant and anti-drip polyester fabric.

[0032] The structure of the phosphite flame retardant obtained in step S1 was confirmed, and the 1H NMR data are as follows: ¹H NMR (400 MHz, DMSO) δ 7.59 (s, 1H), 5.79 (s, 1H), 4.07 – 3.94 (m, 5H), 3.68 (s, 5H), 3.55 (s, 5H), 3.40 (s, 2H), 2.81 (s, 9H), 2.61 (s, 2H), 1.91 – 1.75 (m, 1H). ¹³C NMR (101 MHz, DMSO) δ 61.73, 58.99, 43.35. Phosphorus spectrum data: 31P NMR (162 MHz, DMSO) δ 3.11, 2.71. Example 2 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0033] The specific steps are basically the same as in Example 1, except that the mass concentration of phosphite flame retardant in the finishing solution is 15% and the mass concentration of pentaerythritol is 6%.

[0034] Example 3 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0035] The specific steps are basically the same as in Example 1, except that the mass concentration of phosphite flame retardant in the finishing solution is 25% and the mass concentration of pentaerythritol is 6%.

[0036] Example 4 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0037] The specific steps are basically the same as in Example 1, except that the mass concentration of phosphite flame retardant in the finishing solution is 25% and the mass concentration of glycerol is 6%.

[0038] Example 5 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0039] The process is basically the same as in Example 3, except that pentaerythritol is not added in step (2).

[0040] Example 6 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0041] The process is basically the same as in Example 5, except that in step S1, 0.1 mol of trimethyl phosphite and 0.1 mol of ethanolamine are added to a three-necked flask.

[0042] Example 7 This embodiment provides a method for preparing flame-retardant and anti-dripping polyester fabric.

[0043] The process is basically the same as in Example 5, except that in step S1, 0.1 mol of trimethyl phosphite and 0.3 mol of ethanolamine are added to a three-necked flask.

[0044] Comparative Example 1 Use untreated polyester fabric.

[0045] Comparative Example 2 It is basically the same as Example 3, except that step (1) is omitted and phosphite flame retardant is not added in step (2).

[0046] Comparative Example 3 The data is selected from the best performing patent CN 116084163A.

[0047] Combustion experiments were conducted on the flame-retardant and anti-dripping polyester fabrics prepared in Example 3 and Comparative Example 2 of this application. The SEM morphologies before (b)(c) and after (e)(f) combustion are shown below. Figure 2 As shown in the image, a comparison of SEM images of flame-retardant and anti-dripping polyester fabrics before and after combustion clearly shows that the char layer formed by polyester fabric treated only with phosphite flame retardant is denser than that of untreated polyester fabric, but still has a few pores. In contrast, polyester fabric treated with composite flame retardant forms a continuous and dense char layer, which is the reason for its excellent anti-dripping performance. In addition, the char layer surface has a large number of bubbly protrusions, indicating that the flame retardant plays a role in both the condensed phase and the gas phase, resulting in the excellent flame-retardant performance of the treated polyester fabric.

[0048] The limiting oxygen index (LOI:%) and damaged length of the flame-retardant and anti-drip polyester fabrics prepared in Examples 1-4 and Comparative Examples 1-2 of this application were tested, and the results are shown in Table 1 below. The test conditions are as follows: Limiting oxygen index (LOI) test: According to GB / T5454-1997 "Determination of Burning Performance of Textiles - Oxygen Index Method", this test method involves placing the sample under vertical test conditions in an oxygen-nitrogen mixed gas flow to determine the lowest oxygen concentration (also known as the limiting oxygen index) that just sustains combustion. The sample is clamped in a sample holder and placed vertically inside a combustion chamber. The upper part of the sample is ignited in an upward-flowing oxygen-nitrogen gas flow, and its combustion characteristics are observed. The afterburning time (not exceeding 2 minutes) or destruction length (not exceeding 40 mm) is compared with the specified limiting value. By testing a series of samples at different oxygen concentrations, the lowest oxygen concentration, expressed as the percentage of oxygen required to sustain combustion, can be determined.

[0049] The length of the fabric damaged was determined in accordance with GB / T5455-2014 standard "Determination of vertical damage length, smoldering and afterflame time of textiles".

[0050] Table 1.

[0051] As shown in Table 1, the flame retardant properties of flame-retardant and anti-dripping polyester fabrics are as follows: limiting oxygen index (LOI) of 25.7%-28.8%, damage length of 4.1cm-9.3cm, and no dripping (the LOI of untreated polyester fabric is 18.5%, the damage length is 21.6cm, and dripping occurs). In contrast, the lowest damage length in the vertical burning test of patent CN 116084163A was 10.1 cm, and the flame-retardant finishing of that patent used phosphorus trichloride, so chlorine may still be present on the fabric after finishing, and halogens are not environmentally friendly. In contrast, the lowest vertical burning damage length of this patent is only 4.1 cm, and it uses a halogen-free flame retardant, which is more environmentally friendly. The LOI of polyester fabrics treated with a composite flame retardant prepared with 15% or more phosphite flame retardant and 6% polyol was 27.2%, 28.6%, and 28.8%, respectively, all greater than 27% (meeting the standard for flame-retardant textiles, i.e., LOI>27%). As can be seen from the results of Example 5, the LOI of polyester fabrics treated only with phosphite flame retardant was only 25.7%, but it still had excellent anti-dripping effect.

[0052] Table 2 shows the LOI data of polyester fabrics treated with the products obtained from the reaction of trimethyl phosphite and ethanolamine at different molar ratios (without the addition of pentaerythritol).

[0053] Table 2.

[0054] For any points not covered above, existing technologies shall apply.

[0055] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a flame-retardant and anti-drip polyester fabric, characterized in that, The specific steps include the following: S1. Preparation of phosphite flame retardants, the specific preparation method is as follows: A transesterification reaction was carried out between trialkyl phosphite and ethanolamine at a molar ratio of 1:1.5 to 1:2.5, at a reaction temperature of 80℃ to 180℃, and for a reaction time of 4 to 18 hours. Unreacted trimethyl phosphite was then removed by distillation to obtain a finishing flame retardant, namely, a phosphite flame retardant. This finishing flame retardant is a mixture, and its general compound formula is shown in Formula I. Equation I, where n is 0, 1, or 2; S2. The phosphite flame retardant obtained in S1 is mixed with a polyol to obtain a composite flame retardant. The composite flame retardant is dissolved in water and stirred evenly to obtain a finishing solution. The polyol is pentaerythritol or glycerol. S3. Pre-treat the surface of the polyester fabric with sodium hydroxide solution; S4. The pretreated polyester fabric is immersed in the finishing solution described in S2, and after drying, flame-retardant and anti-dripping polyester fabric is obtained.

2. The preparation method according to claim 1, characterized in that, The phosphite flame retardant in the finishing solution has a mass concentration of 5% to 40%, and the polyol has a mass concentration of 4% to 15%.

3. The preparation method according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 1 mol / L.

4. The preparation method according to claim 1, characterized in that, The immersion treatment time is 2-6 hours; the bath ratio is 1:10 to 1:20; the drying treatment temperature is 60℃ to 100℃; and the time is 10 minutes to 30 minutes.

5. A flame-retardant and anti-drip polyester fabric prepared by the preparation method according to any one of claims 1-4.

6. The flame-retardant and anti-dripping polyester fabric as described in claim 5, characterized in that, The limiting oxygen index of the flame-retardant and anti-dripping polyester fabric is 25.7%~28.8%, and the damaged length is 4.1cm~9.3cm.

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