Preparation method of flame-retardant fiber

Abstract

The embodiment of the invention discloses a preparation method of flame-retardant fiber, which comprises the following steps: mixing a matrix material, a flame retardant, a compatilizer and a coupling agent to form a premix, the matrix material being polypropylene fragments or particles; putting the premix into a double-screw extruder to generate flame-retardant polypropylene composite material particles; the flame-retardant polypropylene composite material particles are subjected to chemical crosslinking, melting, spinning, cooling, stretching and winding to generate flame-retardant fibers.

Description

Technical Field

[0001] This specification relates to the field of flame retardant fiber technology, and in particular to a method for preparing flame retardant fibers. Background Technology

[0002] Flame-retardant fibers, as a type of textile material with special properties, are difficult to ignite when in contact with a fire source, or they self-extinguish after being removed from the fire source, thus slowing the spread of flames. Therefore, flame-retardant fibers play a crucial role in industrial protection and firefighting, effectively preventing the spread of fires and ensuring personnel safety.

[0003] Blending modification is an important process for preparing flame-retardant fibers. In this method, flame retardants are physically mixed with the polymer melt or solution before spinning, and then the fibers are produced through conventional melt spinning or wet spinning processes. During this process, fine flame retardant powders with good compatibility with the polymer matrix are uniformly dispersed into the molten polymer (such as polypropylene, polyethylene, etc.) or polymer solution. When the fibers are exposed to high temperatures, these flame retardants exert their flame-retardant effect through various mechanisms, including endothermic decomposition, dilution of flammable gases, and covering to isolate oxygen. Commonly used blending flame retardants include inorganic hydroxides (such as aluminum hydroxide and magnesium hydroxide), phosphorus-based flame retardants, nitrogen-based flame retardants, and composite flame retardants.

[0004] The advantages of blending are its relatively simple production process, minimal need for modification of existing spinning production lines, wide applicability, and good cost-effectiveness. However, its limitations lie in the fact that if the flame retardant and polymer are not compatible, it may affect the stability of the spinning process and the final strength and feel of the fiber. Some flame retardants may also pose a risk of migration or precipitation, and their flame retardant effect may decrease to some extent after repeated washing.

[0005] Based on this, this application provides a method for preparing flame-retardant fibers. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the embodiments in this specification are implemented as follows: This specification provides a method for preparing flame-retardant fibers to address the following issues: In the prior art, flame-retardant fibers produced using blending modification methods may suffer from poor compatibility between the flame retardant and the polymer, potentially affecting the stability of the spinning process and the final strength and feel of the fiber. Furthermore, some flame retardants may be at risk of migration or precipitation, and the flame-retardant effect may decrease to some extent after repeated washing.

[0007] This specification provides an embodiment of a method for preparing flame-retardant fibers, the method comprising: A premix is ​​formed by mixing a matrix material, a flame retardant, a compatibilizer, and a coupling agent, wherein the matrix material is polypropylene fragments or granules. The premixed material is fed into a twin-screw extruder to generate flame-retardant polypropylene composite material particles; The flame-retardant polypropylene composite material particles are chemically cross-linked, then melted, spun, cooled, stretched, and wound to form flame-retardant fibers.

[0008] Furthermore, the mixing of the matrix material, flame retardant, compatibilizer, and coupling agent to form a premix specifically includes: The flame retardant is surface-treated with a coupling agent to obtain a surface-modified flame retardant, wherein the weight percentage of the coupling agent to the matrix material is 1~8:100, and the weight percentage of the flame retardant to the matrix material is 15~25:100. The matrix material, the compatibilizer, and the surface-modified flame retardant are mixed to form a premix, wherein the weight percentage of the compatibilizer to the matrix material is 3~10:100.

[0009] Furthermore, the coupling agent is a silane coupling agent or a titanate coupling agent; The flame retardant is a phosphorus-nitrogen intumescent flame retardant. The compatibilizer is maleic anhydride-grafted polypropylene.

[0010] Furthermore, the premix also includes a smoke suppressant, which is ammonium polyphosphate or zinc borate, and the weight percentage of the smoke suppressant to the matrix material is 1~8:100; The premix further includes an antioxidant, wherein the antioxidant is pentaerythritol tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl]propionate; The antioxidant to the matrix material has a weight percentage of 0.1~0.5:100.

[0011] Furthermore, the antioxidant also includes: a phosphite antioxidant, wherein the phosphite antioxidant is tris[2,4-di-tert-butylphenyl]phosphite; The weight percentage of the phosphite antioxidant to the matrix material is 0.05~0.2:100.

[0012] Further, the step of feeding the premixed material into a twin-screw extruder to generate flame-retardant polypropylene composite material particles specifically includes: The premixed material is fed into a twin-screw extruder, and the temperature of the conveying section of the twin-screw extruder is set to 150~180℃, the temperature of the compression section to 180~200℃, the temperature of the melting section to 200~220℃, the temperature of the mixing section to 220~240℃, the temperature of the exhaust section to 210℃, and the temperature of the die head area to 200℃.

[0013] Further, the step of feeding the premixed material into a twin-screw extruder to generate flame-retardant polypropylene composite material particles further includes: Long glass fibers are added to the side feed port of the melting section of the twin-screw extruder.

[0014] Furthermore, the screw speed of the twin-screw extruder is 400~450 r / min.

[0015] Furthermore, the chemical crosslinking uses a peroxide crosslinking agent, specifically dicumyl peroxide; The amount of the peroxide crosslinking agent added is 0.5% to 3% of the matrix material, and the crosslinking temperature of the peroxide crosslinking agent is 155 to 180°C.

[0016] Furthermore, the preparation method further includes: The flame-retardant fiber is blended with an ethylene-vinyl acetate copolymer to obtain a composite flame-retardant material; The composite flame-retardant material is subjected to hydrophilic and antistatic treatments to obtain the final flame-retardant material.

[0017] The above-mentioned at least one technical solution adopted in the embodiments of this specification can achieve the following effective effects: by mixing the matrix material, flame retardant, compatibilizer and coupling agent to form a premix, wherein the matrix material is polypropylene fragments or granules; the premix is ​​fed into a twin-screw extruder to generate flame-retardant polypropylene composite material granules; after the flame-retardant polypropylene composite material granules are chemically cross-linked, they are melted, spun, cooled, stretched and wound to generate flame-retardant fibers. It can effectively modify the flame retardant properties of recycled polypropylene, while considering the compatibility, antioxidant properties and mechanical properties of the reinforcing material during the modification process, thereby increasing the flame retardant properties and achieving a better flame retardant effect. It can also overcome the problem of static electricity in traditional flame-retardant fibers and obtain antistatic flame-retardant fibers. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for preparing flame-retardant fibers provided in the embodiments of this specification; Figure 2 This is a flowchart illustrating another method for preparing flame-retardant fibers provided in the embodiments of this specification. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0021] Unless otherwise specified, the experimental methods used in the embodiments of this specification are conventional methods. Unless otherwise specified, all experimental materials used are commercially available.

[0022] This specification provides a method for preparing flame-retardant fibers through its embodiments. Figure 1 This is a flowchart illustrating a method for preparing flame-retardant fibers, as provided in the embodiments of this specification. Figure 1 As shown, the preparation method includes: Step S101: Mix the matrix material, flame retardant, compatibilizer and coupling agent to form a premix, wherein the matrix material is polypropylene fragments or granules.

[0023] In the embodiments described in this specification, the matrix material can be obtained by blending modification or by polymerization. The methods for obtaining the matrix material utilize existing technologies and will not be elaborated upon here.

[0024] In the embodiments of this specification, the mixing of the matrix material, flame retardant, compatibilizer, and coupling agent to form a premix specifically includes: The flame retardant is surface-treated with a coupling agent to obtain a surface-modified flame retardant, wherein the weight percentage of the coupling agent to the matrix material is 1~8:100, and the weight percentage of the flame retardant to the matrix material is 15~25:100. The matrix material, the compatibilizer, and the surface-modified flame retardant are mixed to form a premix, wherein the weight percentage of the compatibilizer to the matrix material is 3~10:100.

[0025] When heated, flame retardants can form an expanded char layer, thus providing heat insulation and oxygen barrier properties for flame retardancy. The presence of coupling agents can modify the surface of the flame retardant, thereby ultimately improving the compatibility between the flame retardant and the matrix material and enhancing the flame retardant effect.

[0026] In the embodiments of this specification, the weight percentage of coupling agent to matrix material is preferably 4:100, the weight percentage of compatibilizer to matrix material is preferably 7:100, and the weight percentage of flame retardant to matrix material is preferably 21:100.

[0027] In the embodiments described in this specification, the coupling agent is a silane coupling agent or a titanate coupling agent; The flame retardant is a phosphorus-nitrogen intumescent flame retardant. The compatibilizer is maleic anhydride-grafted polypropylene.

[0028] The presence of compatibilizers can improve the compatibility between flame retardants and matrix materials, thereby enhancing the stability of flame retardant materials and improving their flame retardant effect.

[0029] In the embodiments of this specification, the premix further includes: a smoke suppressant, wherein the smoke suppressant is ammonium polyphosphate or zinc borate, and the weight percentage of the smoke suppressant to the matrix material is 1~8:100; The premix further includes an antioxidant, wherein the antioxidant is pentaerythritol tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl]propionate; The antioxidant to the matrix material has a weight percentage of 0.1~0.5:100.

[0030] Smoke suppressants reduce smoke production during combustion through chemical reactions. Ammonium polyphosphate (APP) works by decomposing at high temperatures to form a heat-insulating char layer, simultaneously inhibiting the generation of smoke and toxic gases. When heated above 285°C, APP decomposes to produce phosphoric acid and ammonia. The phosphoric acid further dehydrates to form polymetaphosphoric acid, promoting dehydration and carbonization of the material surface, forming a porous, expanded char layer. This char layer effectively isolates oxygen and heat transfer, delaying the material from reaching its ignition point.

[0031] Zinc borate is an environmentally friendly, non-halogenated flame retardant with multiple functions including flame retardancy, char formation, and smoke suppression. Specifically, zinc borate decomposes upon heating to produce boron trichloride and water vapor, which dilutes combustible gases and inhibits smoke formation. The boric acid produced during decomposition promotes the formation of a dense char layer on the material surface, reducing the escape of combustibles. At the same time, zinc compounds guide the formation of aliphatic char rather than aromatic compounds, further reducing smoke density.

[0032] In the embodiments of this specification, the weight percentage of smoke suppressant to matrix material is preferably 6:100, and the weight percentage of antioxidant to matrix material is preferably 0.2:100.

[0033] In the embodiments of this specification, the antioxidant further includes: a phosphite antioxidant, wherein the phosphite antioxidant is tris[2,4-di-tert-butylphenyl]phosphite; The weight percentage of the phosphite antioxidant to the matrix material is 0.05~0.2:100.

[0034] In the process of preparing flame-retardant fibers, antioxidants are added, mainly to delay the performance degradation of the material caused by oxidation.

[0035] In the embodiments described in this specification, the weight percentage of phosphite antioxidant to matrix material is preferably 0.2:100.

[0036] Step S103: The premixed material is fed into a twin-screw extruder to generate flame-retardant polypropylene composite material particles.

[0037] In the embodiments of this specification, the step of feeding the premixed material into a twin-screw extruder to generate flame-retardant polypropylene composite material particles specifically includes: The premixed material is fed into a twin-screw extruder, and the temperature of the conveying section of the twin-screw extruder is set to 150~180℃, the temperature of the compression section to 180~200℃, the temperature of the melting section to 200~220℃, the temperature of the mixing section to 220~240℃, the temperature of the exhaust section to 210℃, and the temperature of the die head area to 200℃.

[0038] Temperature control is crucial for ensuring uniform plasticization and fiber properties. In this embodiment, segmented temperature control of the twin-screw extruder helps the material melt gradually, mix thoroughly, and prevents material degradation or migration due to excessively high temperatures.

[0039] Because fiber breakage due to excessive shearing may occur during processing in a twin-screw extruder, in this embodiment, to prevent fiber breakage due to excessive shearing, long glass fibers are further added to the side feed port of the melting section of the twin-screw extruder. This allows the long glass fibers to be fully impregnated and mixed with the molten polypropylene matrix, preventing excessive shearing and breakage of the fibers in the conveying section, thus ensuring fiber length and mechanical properties, and significantly improving the strength of the composite material. The molten mixture is cooled in a water bath and pelletized in a granulator to obtain flame-retardant polypropylene composite material particles.

[0040] In the embodiments of this specification, the step of feeding the premixed material into a twin-screw extruder to generate flame-retardant polypropylene composite material particles further includes: Long glass fibers are added to the side feed port of the melting section of the twin-screw extruder.

[0041] In the embodiments described in this specification, the screw speed of the twin-screw extruder is 400~450 r / min.

[0042] In the embodiments described in this specification, the amount of long glass fiber added is 30%.

[0043] In the embodiments of this specification, the chemical crosslinking uses a peroxide crosslinking agent, and the peroxide crosslinking agent is dicumyl peroxide; The amount of the peroxide crosslinking agent added is 0.5% to 3% of the matrix material, and the crosslinking temperature of the peroxide crosslinking agent is 155 to 180°C.

[0044] Controlling the screw speed of a twin-screw extruder can ensure that the flame retardant is evenly dispersed and reduce agglomeration.

[0045] Step S105: After chemical cross-linking, the flame-retardant polypropylene composite material particles are melted, spun, cooled, stretched and wound to generate flame-retardant fibers.

[0046] Although the method described above can produce flame-retardant fibers, the resulting flame-retardant fibers have a poor hand feel and are prone to static electricity.

[0047] In the embodiments of this specification, the preparation method further includes: The flame-retardant fiber is blended with an ethylene-vinyl acetate copolymer to obtain a composite flame-retardant material; The composite flame-retardant material is subjected to hydrophilic and antistatic treatments to obtain the final flame-retardant material.

[0048] Figure 2 This is a flowchart illustrating another method for preparing flame-retardant fibers provided in the embodiments of this specification.

[0049] Step S201: Mix the matrix material, flame retardant, compatibilizer and coupling agent to form a premix, wherein the matrix material is polypropylene fragments or granules.

[0050] Step S203: The premixed material is fed into a twin-screw extruder to generate flame-retardant polypropylene composite material particles.

[0051] Step S205: After chemical cross-linking, the flame-retardant polypropylene composite material particles are melted, spun, cooled, stretched and wound to generate flame-retardant fibers.

[0052] Step S207: Blend the flame-retardant fiber with ethylene-vinyl acetate copolymer to obtain a composite flame-retardant material.

[0053] Step S207 overcomes the problem of poor hand feel of flame-retardant fibers, improving fiber softness while ensuring flame retardancy.

[0054] Step S209: Perform hydrophilic treatment and antistatic treatment on the composite flame retardant material to obtain the final flame retardant material.

[0055] To further enhance the feel of flame-retardant fibers, a hydrophilic treatment is performed, introducing hydrophilic groups, which reduces the coefficient of friction on the fiber surface and improves the fabric's touch.

[0056] In specific embodiments, the hydrophilic treatment method may employ plasma treatment or coating technology. The specific techniques used in the hydrophilic treatment method may be existing technologies, and the specific methods used in the hydrophilic treatment do not constitute a limitation of this application.

[0057] While hydrophilic treatment can reduce the surface friction coefficient of fibers to some extent, its antistatic effect is limited. To achieve a truly effective antistatic effect, the embodiments in this specification perform antistatic treatment on top of the hydrophilic treatment to obtain the final flame-retardant fibers. During the antistatic treatment, an ethylene oxide condensate-based antistatic agent is used for surface treatment, thereby solving the antistatic problem while improving the feel.

[0058] To further verify the performance of the flame-retardant fibers provided in the embodiments of this specification, several further embodiments are provided in this specification for performance testing.

[0059] Example 1: 100 parts matrix material, 4 parts coupling agent, 21 parts flame retardant, 7 parts compatibilizer, 30% long glass fiber; Example 2: 100 parts matrix material, 4 parts coupling agent, 21 parts flame retardant, 7 parts compatibilizer, 30% long glass fiber, and 6 parts smoke suppressant. Example 3: 100 parts matrix material, 4 parts coupling agent, 21 parts flame retardant, 7 parts compatibilizer, 30% long glass fiber, 6 parts smoke suppressant, and 0.2 parts antioxidant; Example 4: A commercially available flame-retardant fiber material.

[0060] The test results are shown in Table 1.

[0061] Table 1: Test Result Statistics

[0062] In Table 1, thermal stability was tested by strength retention rate after the flame-retardant fiber was treated at 120°C for 24 hours. The higher the strength retention rate, the more stable the thermal stability.

[0063] As can be seen from the test results in Table 1, the flame-retardant fiber provided in the embodiments of this specification has significantly improved performance compared with the prior art.

[0064] The method for preparing flame-retardant fibers provided in the embodiments of this specification involves mixing a matrix material, a flame retardant, a compatibilizer, and a coupling agent to form a premix, wherein the matrix material is polypropylene fragments or granules; the premix is ​​fed into a twin-screw extruder to generate flame-retardant polypropylene composite material granules; after chemical cross-linking, the flame-retardant polypropylene composite material granules are melted, spun, cooled, stretched, and wound to generate flame-retardant fibers. This method can effectively modify recycled polypropylene for flame retardancy, while considering compatibility, antioxidant properties, and mechanical properties of reinforcing materials during the modification process, thereby increasing flame retardant performance and achieving better flame retardant effects. Furthermore, it can overcome the problem of static electricity generation in traditional flame-retardant fibers, resulting in antistatic flame-retardant fibers.

[0065] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0066] The above description is merely an embodiment of this specification and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A process for the production of flame-retardant fibres, characterised in that, The preparation method comprises: Mixing a base material, a flame retardant, a compatibilizer and a coupling agent to form a premix, wherein the base material is polypropylene chips or particles; Putting the premix into a double screw extruder to generate flame-retardant polypropylene composite particles; After the flame-retardant polypropylene composite particles are chemically crosslinked, they are melted, spun, cooled, stretched and wound to generate flame-retardant fibers.

2. The production method according to claim 1, wherein The mixing of the base material, the flame retardant, the compatibilizer and the coupling agent to form the premix specifically comprises: Surface treating the flame retardant with the coupling agent to obtain a surface-modified flame retardant, wherein the weight percentage of the coupling agent to the base material is 1-8:100, and the weight percentage of the flame retardant to the base material is 15-25:100; Mixing the base material, the compatibilizer and the surface-modified flame retardant to form the premix, wherein the weight percentage of the compatibilizer to the base material is 3-10:

100.

3. The production method according to claim 2, wherein The coupling agent is a silane coupling agent or a titanate coupling agent; The flame retardant is a phosphorus-nitrogen intumescent flame retardant; The compatibilizer is maleic anhydride grafted polypropylene.

4. The production method according to claim 1, wherein The premix further comprises a smoke suppressant, wherein the smoke suppressant is ammonium polyphosphate or zinc borate, and the weight percentage of the smoke suppressant to the base material is 1-8:100; The premix further comprises an antioxidant, wherein the antioxidant is pentaerythritol tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl]propionate; The weight percentage of the antioxidant to the base material is 0.1-0.5:

100.

5. The production method according to claim 4, wherein The antioxidant further comprises a phosphite antioxidant, wherein the phosphite antioxidant is tris[2,4-di-tert-butylphenyl] phosphite; The weight percentage of the phosphite antioxidant to the base material is 0.05-0.2:

100.

6. The production method according to claim 1, wherein The putting of the premix into the double screw extruder to generate the flame-retardant polypropylene composite particles specifically comprises: The premix is put into the double screw extruder, and the temperature of the conveying section of the double screw extruder is set to 150-180℃, the temperature of the compression section is set to 180-200℃, the temperature of the melting section is set to 200-220℃, the temperature of the mixing section is set to 220-240℃, the temperature of the exhaust section is set to 210℃, and the temperature of the die zone is set to 200℃.

7. The production method according to claim 6, wherein The putting of the premix into the double screw extruder to generate the flame-retardant polypropylene composite particles further comprises: Long glass fibers are added to the side feeding port of the melting section of the double screw extruder.

8. The production method according to claim 1, wherein The rotation speed of the screw of the double screw extruder is 400-450 r / min.

9. The production method according to claim 1, wherein The chemical crosslinking uses a peroxide crosslinking agent, and the peroxide crosslinking agent is dicumyl peroxide; The addition amount of the peroxide crosslinking agent is 0.5%-3% of the base material, and the crosslinking temperature of the peroxide crosslinking agent is 155-180℃.

10. The production method according to claim 1, wherein The preparation method further comprises: Blending the flame-retardant fibers with ethylene-vinyl acetate copolymer to obtain a composite flame-retardant material; Performing hydrophilic treatment and antistatic treatment on the composite flame-retardant material to obtain a final flame-retardant material.

Images