Flame retardant cellulose fiber and flame retardant fabric

Abstract

The present invention belongs to the technical field of cellulose fiber processing and fabrics, and specifically relates to a flame-retardant cellulose fiber and a flame-retardant fabric. The present invention utilizes the hydroxyl groups of cellulose fibers to first covalently graft boric acid, and then utilizes the two remaining active hydroxyl groups of boric acid to covalently bind melamine and tannic acid respectively to perform post-spinning modification of the cellulose fibers. This technology improves the flame retardancy of cellulose fibers, while also improving the mechanical properties of cellulose fibers, and enables the fibers to achieve self-coloring without the need for subsequent dyeing steps, thereby exerting comprehensive advantages in terms of flame retardancy, mechanical properties, aesthetics, environmental protection, etc., and the resulting fibers have good softness and elasticity, etc., and have good economic value and social benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of cellulose fiber processing and fabrics, and in particular relates to flame-retardant cellulose fiber and flame-retardant fabrics. Background Art

[0002] As an important functional material, flame-retardant cellulose fiber has been widely used in many fields. At present, the preparation technologies of flame-retardant cellulose fiber and flame-retardant fabric include blending technology (adding flame retardant by injection method before spinning, which belongs to pre-spinning modification. The flame retardant is required to have suitable acidity and alkalinity, good dispersibility and particle size; and consistent with the solubility of cellulose, otherwise it cannot be evenly dispersed, which seriously affects the mechanical properties of the fabric), finishing technology (adding flame retardant or chemical grafting to the spun fibers or fabrics after forming through grafting, coating, rolling-baking-baking, layer-by-layer self-assembly and other methods) (Guo Xun. Preparation and performance research of flame-retardant cellulose fibers. Tianjin University of Technology 2021 degree thesis).

[0003] Patent CN114182527A discloses a method for preparing a durable flame retardant finishing liquid and a bio-based phytic acid durable flame retardant cotton fabric, wherein polyethyleneimine and crosslinking agent EH (finishing liquid A), crosslinking agent EH (finishing liquid B) and phytic acid (finishing liquid C) are used to finish the cotton fabric, respectively, to give the cotton fabric durable flame retardant properties. Patent CN114703667A discloses a method for preparing a flame retardant cotton fabric based on attapulgite layer-by-layer self-assembly technology, wherein polyethyleneimine, attapulgite and phytic acid are finished on the cotton fabric by a layer-by-layer self-assembly method to prepare a flame retardant cotton fabric. However, the above technical processes cause serious damage to the physical properties of cotton fabrics, such as strong damage. Patent CN108823667A discloses a manufacturing process for regenerated flame-retardant cellulose fibers with a multi-element synergistic flame retardant. The regenerated flame-retardant cellulose fibers produced have high strength and good weaving performance. However, toxic organic solvents are used in the preparation process. Patent CN102345174A discloses a method for preparing flame-retardant spun viscose, but the product produced is conventional primary color flame-retardant viscose fiber, which needs to be dyed with a dye later.

[0004] Therefore, although the above methods can prepare specific flame-retardant cellulose fibers, there are still many problems such as low strength of the prepared cellulose fibers, polluted solvents in the preparation process, and the products are all conventional colorless flame-retardant fibers that still require subsequent coloring steps. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a flame retardant cellulose fiber and a flame retardant fabric. To achieve this object, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a flame retardant cellulose fiber, wherein the preparation method thereof comprises the following steps:

[0007] S1: Boric acid and cellulose fiber are heated to react in a solvent to prepare boric acid grafted cellulose fiber;

[0008] S2: heating the boric acid grafted cellulose fiber obtained in step S1 with melamine and tannic acid in a solvent for reaction, and drying to obtain flame retardant cellulose fiber.

[0009] The main technical principles for preparing the flame retardant cellulose fiber are as follows: Figure 1 .

[0010] The main principle of the above preparation method is to use the hydroxyl groups on cellulose fibers to undergo an esterification reaction with boric acid to obtain boric acid-grafted cellulose fibers; and then use the remaining two active hydroxyl groups of boric acid to covalently bind to melamine and tannic acid respectively. However, there are many covalent binding sites in the reaction process, and other reaction byproducts are inevitably present, such as two active hydroxyl groups of one molecule of boric acid binding to two molecules of melamine respectively.

[0011] The above preparation method adopts the post-spinning modification of cellulose fibers.

[0012] Preferably, in step S1, the mass ratio of cellulose fiber to boric acid is 1: (0.25-2);

[0013] Preferably, in step S2, the mass ratio of cellulose fiber to melamine is 1:(0.5-3); the mass ratio of cellulose fiber to tannic acid is 1:(1-4);

[0014] Preferably, the solvents used in the reactions of steps S1 and S2 are both water.

[0015] Preferably, the pH value of the reaction in step S1 is 9-10;

[0016] Preferably, the pH value of the reaction in step S2 is 5-6.

[0017] Preferably, in step S1, the reaction temperature is 60°C to 80°C, and the reaction time is 1h to 4h;

[0018] Preferably, in step S2, the reaction temperature is 70°C to 90°C, and the reaction time is 2h to 5h;

[0019] Preferably, in step S1, the cellulose fiber is regenerated cellulose fiber; further preferably, the specification of the regenerated cellulose fiber is 2.5 dtex to 5.5 dtex; further preferably, the cellulose is cellulose pulp with a degree of polymerization of 600 to 1800, and the α-cellulose content in the cellulose pulp is ≥ 90%; further preferably, the cellulose pulp is selected from one or more of cotton pulp, wood pulp, bamboo pulp, hemp pulp, straw pulp, and waste residue pulp;

[0020] In a first aspect, the present invention provides a flame retardant fabric comprising the flame retardant cellulose fiber.

[0021] Preferably, the flame retardant fabric is any one of clothing fabric and indoor and outdoor decorative fabric.

[0022] The technology of the present invention has the following beneficial effects

[0023] 1. The flame-retardant cellulose fiber of the present invention does not contain halogen flame retardants. Instead, a specific grafting reaction sequence is used to achieve uniform bonding of boric acid-melamine, boric acid-tannic acid and hydroxyl groups on cellulose fibers, achieving synergistic flame retardant effects of the three. The loading rate of the flame retardant reaches 9.2% to 12.7%.

[0024] This grafting method results in a special molecular arrangement of melamine, boric acid, and tannic acid on cellulose fibers; the outer layer molecules are melamine / tannic acid, and the inner layer is boric acid. This rationally utilizes the buffering and dilution effect of the combustible gas in the outer layer and the cooling and isolation effect of the boron oxide in the inner layer, and exerts a uniform, stable and significant flame retardant effect, improving the fire resistance and safety of the fiber material. The limiting oxygen index (LOI) value (%) of the resulting flame retardant cellulose fiber is 7~9 higher than that of the original fiber.

[0025] The flame-retardant cellulose fibers obtained by this method have improved strength, etc., and can effectively overcome the problems of poor strength of cellulose fibers caused by covalent grafting modification after spinning. The tensile strength is increased by 5% to 12.5% ​​compared with the original fibers.

[0026] 2. The present invention adopts post-spinning modification technology to prepare flame-retardant cellulose fibers. Water is used as a solvent during the preparation, thereby avoiding the pollution to the environment caused by the use of organic solvents. This not only contributes to environmental protection, but also meets the standards and requirements of green production.

[0027] 3. The flame-retardant cellulose fiber of the present invention has its own color, and no additional dyeing step is required, thereby reducing the environmental pollution of the textile dyeing step. This is because a stable conjugated color system is formed on the surface of the cellulose fiber. This color not only provides an intuitive and aesthetically pleasing color identification for the fiber, but also is more in line with the green preparation concept because it eliminates the additional dyeing step. In addition, tannic acid itself is yellow-brown and melamine boric acid itself is white. The cellulose fiber obtained by the preparation method of the present invention also overcomes the problem of mixed fiber color caused by ternary compounds caused by other preparation methods; thus, the three can be used for fiber fabrics, especially clothing textiles, indoor or outdoor decorative / renovation textiles, and meet aesthetic requirements.

[0028] Therefore, the flame-retardant cellulose fiber of the present invention has flame retardancy, mechanical properties, aesthetic advantages, and green environmental protection advantages brought by not using organic solvents and not requiring additional dyeing processes.

[0029] 4. The method for preparing flame-retardant cellulose fibers of the present invention can be effectively applied to various types of cellulose fibers, such as cotton fibers, linen fibers, viscose fibers, lyocell fibers and fabrics thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a main technical principle diagram for preparing the flame-retardant cellulose fiber of the present invention;

[0031] Figure 2 is a scanning electron microscope image of the comparative example cellulose fiber;

[0032] Figure 3 is a scanning electron microscope image of the cellulose fiber of Example 3;

[0033] Figure 4 This is a product photo of comparative cellulose fiber;

[0034] Figure 5 This is a product photo of the cellulose fiber of Example 3;

[0035] Figure 6 It is the infrared spectra of the cellulose fibers of the comparative example and embodiment 3. DETAILED DESCRIPTION

[0036] The technical ideas, solutions, effects, etc. of the present invention are described in detail below through specific embodiments in conjunction with the accompanying drawings. The embodiments are only exemplary descriptions of the present invention and are not to be regarded as limiting the protection scope of the present invention.

[0037] Main raw materials: The cellulose fiber used in the following examples is regenerated cellulose fiber prepared from pulp with a degree of polymerization of 1200, with a specification of 4 dtex; Boric acid: chemically pure, purity ≥99.5%, purchased from Shanghai Titan Technology Co., Ltd.; Sodium hydroxide: chemically pure, purity 97%, purchased from Shanghai Titan Technology Co., Ltd.; Melamine: chemically pure, purchased from Shanghai Titan Technology Co., Ltd.; Tannic acid: chemically pure, purchased from Shanghai Titan Technology Co., Ltd.; Acetic acid: chemically pure, purity 99%, purchased from Shanghai Titan Technology Co., Ltd.

[0038] The main technical principle diagram of the preparation of the flame retardant cellulose fiber of the present invention is shown in Figure 1; This preparation method belongs to post-spinning modification. The main principle is to use the hydroxyl groups on cellulose fibers to react with boric acid for esterification, thereby obtaining boric acid-grafted cellulose fibers; and then use the remaining two active hydroxyl groups of boric acid to covalently bind with melamine and tannic acid respectively. However, there are many covalent binding sites in the reaction process, and other reaction by-products are inevitably present, such as two active hydroxyl groups of one molecule of boric acid binding to two molecules of melamine respectively.

[0039] Example 1 A flame retardant cellulose fiber

[0040] This embodiment provides a method for preparing flame-retardant cellulose fibers, the steps of which are as follows:

[0041] S1. Weigh 0.31g of boric acid, add water to prepare a 2wt% aqueous solution, adjust the pH to 9-10 with sodium hydroxide, add 0.81g of cellulose fiber, react at 60°C for 1h, take out the cellulose fiber, wash it with pure water and dry it;

[0042] S2. Weigh 0.63g of melamine, add 50mL of water, dissolve at 80℃, adjust the pH to 5-6 with acetic acid, add 0.85g of tannic acid to dissolve, then add the boric acid-treated cellulose fiber obtained in S1, react at 80℃ for 2h, wash with pure water and dry to obtain flame-retardant cellulose fiber.

[0043] As shown in the feed amounts, in the preparation method, the cellulose fiber:boric acid (w / w) in S1 is about 1:0.38; the cellulose fiber:melamine (w / w) in S2 is about 0.78, and the cellulose fiber:tannic acid (w / w) is about 1:1.04.

[0044] Example 2 A flame retardant cellulose fiber

[0045] This embodiment provides a method for preparing flame-retardant cellulose fibers, the steps of which are as follows:

[0046] S1. Weigh 0.62g of boric acid, add water to prepare a 2wt% aqueous solution, adjust the pH to 9-10 with sodium hydroxide, add 0.81g of cellulose fiber, react at 70°C for 4h, take out the cellulose fiber, wash it with pure water and dry it;

[0047] S2. Weigh 1.26g of melamine, add 100mL of water, dissolve at 80℃, adjust the pH to 5-6 with acetic acid, add 1.70g of tannic acid to dissolve, then add the boric acid-treated cellulose fiber obtained in S1, react at 70℃ for 2h, wash with pure water and dry to obtain flame-retardant cellulose fiber.

[0048] As shown in the feed amounts, in the preparation method, the cellulose fiber: boric acid (w / w) ratio in S1 is about 1:0.76; the cellulose fiber: melamine (w / w) ratio in S2 is about 1.56, and the cellulose fiber: tannic acid (w / w) ratio is about 1:2.09.

[0049] Example 3 A flame retardant cellulose fiber

[0050] This embodiment provides a method for preparing flame-retardant cellulose fibers, the steps of which are as follows:

[0051] S1. Weigh 0.93g of boric acid, add water to prepare a 2wt% aqueous solution, adjust the pH to 9-10 with NaOH, add 0.81g of cellulose fiber, react at 60°C for 2h, take out the cellulose fiber, wash it with pure water and dry it;

[0052] S2. Weigh 1.89g of melamine, add 150mL of water, dissolve at 80℃, adjust the pH to 5-6 with acetic acid, add 2.55g of tannic acid to dissolve, then add the boric acid-treated cellulose fiber obtained in S1, react at 80℃ for 4h, wash with pure water and dry to obtain flame-retardant cellulose fiber.

[0053] As shown in the feed amounts, in the preparation method, the cellulose fiber: boric acid (w / w) in S1 is about 1:1.15; the cellulose fiber: melamine (w / w) in S2 is about 1:2.33, and the cellulose fiber: tannic acid (w / w) is about 1:3.15.

[0054] Example 4 A flame retardant cellulose fiber

[0055] This embodiment provides a method for preparing flame-retardant cellulose fibers, the steps of which are as follows:

[0056] S1. Weigh 0.93g of boric acid, add water to prepare a 2wt% aqueous solution, adjust the pH to 9-10 with sodium hydroxide, add 0.81g of cellulose fiber, react at 80°C for 2h, take out the cellulose fiber, wash it with pure water and dry it;

[0057] S2. Weigh 1.89g of melamine, add 200mL of water, dissolve at 80℃, adjust the pH to 5-6 with acetic acid, add 2.55g of tannic acid to dissolve, then add the boric acid-treated cellulose fiber obtained in S1, react at 90℃ for 3h, wash with pure water and dry to obtain flame-retardant cellulose fiber.

[0058] As shown in the feed amounts, in the preparation method, the cellulose fiber: boric acid (w / w) in S1 is about 1:1.15; the cellulose fiber: melamine (w / w) in S2 is about 1:2.33, and the cellulose fiber: tannic acid (w / w) is about 1:3.15.

[0059] Example 5 Analysis and testing of flame retardant cellulose fibers

[0060] Taking cellulose fibers that have not been flame-retardant modified as a control example, that is, regenerated cellulose fibers prepared from pulp with a degree of polymerization of 1200 and a specification of 4 dtex, scanning electron microscopy analysis, infrared spectrum analysis, energy dispersive X-ray spectroscopy analysis (EDS) and other tests were carried out.

[0061] Part I: Analysis and Characterization of Cellulose Fibers

[0062] Figure 2 and Figure 3 The scanning electron microscope images of the comparative example and Example 3 cellulose fibers respectively show that from a microscopic perspective, no grafts are observed on the surface of the comparative example cellulose fibers; EDS analysis shows that there are only 51.27% C elements and 48.73% O elements on the fiber surface. EDS analysis of the flame-retardant cellulose fibers of Example 3 shows that in addition to C and O elements, there are also B and N elements on the fiber surface, with contents of 3.15% and 11.98% respectively; grafts can be observed on the surface.

[0063] Figure 4 This is a color photo of the comparative cellulose fiber product. Figure 5 This is a color photo of the flame-retardant cellulose fiber product of Example 3. It can be clearly seen that the color of the flame-retardant cellulose fiber of Example 3 has changed significantly, turning into pink. However, the comparative cellulose fiber without flame-retardant modification has no such color change.

[0064] Figure 6 The infrared spectra of the cellulose fibers of the comparative example and Example 3 are shown in FIG. The infrared spectra of the comparative example are shown in FIG. -1 There is a significant -OH stretching vibration absorption peak at 2891cm -1 The absorption peak at 1640 cm is attributed to the stretching vibration of CH, and the bending vibration peaks of -OH and CH appear at 1640 cm -1 and 1367cm -1 1018cm -1 The characteristic peak at is caused by the pyranose ring, a common structure in cellulose.

[0065] In the infrared spectrum of the flame-retardant cellulose fiber of Example 3, the stretching vibration absorption peaks corresponding to -OH and CH still exist, but at 3335 cm -1 The -OH stretching vibration absorption peak of 2892 cm-1 is obviously weakened, which is because some -OH on cellulose reacts with the introduced flame retardant. -1 The absorption peak at 3140cm is greatly enhanced because the introduction of melamine and tannic acid significantly increases CH. -1NH stretching vibration, 1622cm -1 The characteristic absorption peak of CN is 1687cm -1 and 1320cm -1 The absorption bands are O=CO and COC, 1440 cm -1 BN stretching vibration, 1187cm -1 The characteristic absorption of BO proves that the flame retardant component has been successfully grafted onto the surface of cellulose fibers.

[0066] Part 2 Performance testing and analysis of cellulose fibers

[0067] The following are the performance test methods and results of the flame retardant cellulose fibers of the present invention:

[0068] Comparative example: Cellulose fibers that have not been flame-retardant modified were selected, namely, regenerated cellulose fibers prepared from pulp with a degree of polymerization of 1200, with a specification of 4 dtex.

[0069] 1. The test method is as follows:

[0070] (1) Loading rate: The untreated cellulose fibers were placed in an oven and dried at 60°C to 90°C for 4 to 8 hours. The fibers were taken out and weighed. The mass was recorded as m 0 The treated cellulose fibers are dried at 60°C to 90°C for 4 to 8 hours. After being taken out, they are weighed and the mass is recorded as m 1 The flame retardant loading rate of the post-finished cellulose fiber is calculated as follows:

[0071]

[0072] The cellulose fibers in the embodiment and the comparative example are dried at the same temperature and for the same time.

[0073] (2) Limiting oxygen index (LOI): It is assessed in accordance with GB / T 5454-2014 Textile combustion performance test oxygen index method. The textile is woven from fiber bundles with a fiber fineness of 4 dtex and each bundle contains 520 fibers.

[0074] (3) Mechanical properties: The test was conducted in accordance with GB / T19975-2005 “Test method for tensile properties of high-strength filament yarns”. Untwisted fiber bundles were used for the test. Each bundle contained 520 fibers, which were arranged in parallel without overlap.

[0075] 2. The test results are as follows:

[0076] Table 1 Performance comparison between comparative examples and examples

[0077]

[0078] As shown in Table 1, the flame retardant cellulose fiber of the present invention has an extremely high flame retardant loading (up to 9% to 12.7%), so that the flame retardant performance can be better exerted, and the problems of low loading and uneven loading of the blended modification can be overcome; and from the analysis of the limiting oxygen index, the flame retardant cellulose fiber is >26%, which is a flame retardant fiber. The tensile strength of the flame retardant cellulose fiber is improved relative to the cellulose fiber of Comparative Example 1, and the tensile strength improvement rate reaches 5% to 12.5%, which overcomes the problem of reduced tensile strength caused by the existing chemical grafting method to modify the cellulose fiber, and achieves an increase in tensile strength instead of a decrease.

[0079] In addition to the tensile strength test, the elongation at break was further measured. Under the same conditions, the elongation at break of the flame-retardant cellulose fiber of Examples 1-4 was reduced by only 7-20% compared with the original fiber; the elongation at break of the product was about 10-12% (untwisted fiber bundles, each bundle containing 520 fibers, the fibers were arranged in parallel and without overlap), which meets the use requirements. Compared with the post-spinning modification process of cellulose fibers under the same acid-base conditions and reaction time, the elastic attenuation of the obtained cellulose fibers is reduced by 2-7 times (Guo Xun. Preparation and performance study of flame-retardant cellulose fibers. Tianjin University of Technology 2021 thesis).

[0080] The softness of the fibers was further measured using a hand softness tester. The flame retardant finishing of Examples 1-4 had no effect on the softness of the cellulose fibers.

Claims

1. A flame retardant cellulose fiber, characterized in that: The method for preparing the flame retardant cellulose fiber comprises the following steps: S1: Boric acid and cellulose fiber are heated and reacted in a solvent to prepare boric acid grafted cellulose fiber; S2: heating the boric acid grafted cellulose fiber obtained in step S1 with melamine and tannic acid in a solvent for reaction, and drying to obtain flame retardant cellulose fiber.

2. The flame-retardant cellulose fiber according to claim 1, characterized in that: In step S1, the mass ratio of cellulose fiber to boric acid is 1: (0.25-2).

3. The flame-retardant cellulose fiber according to claim 1, characterized in that: In step S2, the mass ratio of cellulose fiber to melamine is 1:(0.5-3); the mass ratio of cellulose fiber to tannic acid is 1:(1-4).

4. The flame-retardant cellulose fiber according to claim 1, characterized in that: The solvents for the reactions in steps S1 and S2 are both water.

5. The flame-retardant cellulose fiber according to claim 1, characterized in that: In the step S1, the pH value of the reaction is 9-10.

6. The flame-retardant cellulose fiber according to claim 1, characterized in that: The pH value of the reaction in step S2 is 5-6.

7. The flame-retardant cellulose fiber according to claim 1, characterized in that: In the step S1, the reaction temperature is 60° C. to 80° C., and the reaction time is 1 h to 4 h.

8. The flame-retardant cellulose fiber according to claim 1, characterized in that: In step S2, the reaction temperature is 70° C. to 90° C., and the reaction time is 2 h to 5 h.

9. The flame-retardant cellulose fiber according to claim 1, characterized in that: In the step S1, the cellulose fiber is regenerated cellulose fiber.

10. A flame retardant fabric, characterized in that: Contains the flame retardant cellulose fiber according to any one of claims 1 to 9.

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