Flame retardant glass fibers, methods of making the same, and fiber reinforced thermoplastic composites

Abstract

This invention belongs to the field of materials technology, and particularly relates to a flame-retardant glass fiber, its preparation method, and fiber-reinforced thermoplastic composite materials. Compared with the prior art, the flame-retardant glass fiber provided by this invention utilizes the large specific surface area of ​​glass fiber to load a flame-retardant coating with a highly efficient flame retardant that rapidly catalyzes char formation, exhibiting a synergistic flame-retardant function. When used in the preparation of fiber-reinforced thermoplastic composite materials, it can promote the char formation of externally added flame retardants at the interface layer between the flame-retardant glass fiber and the resin matrix, achieving a synergistic flame-retardant effect, improving the quality and efficiency of char formation to suppress the wicking effect of the fiber, and enhancing flame-retardant performance. It can reduce the amount of externally added flame retardants used in the granulation process, reducing production costs while also improving mechanical properties, and has broad application prospects in actual industrial production.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and particularly relates to a flame-retardant glass fiber, its preparation method, and fiber-reinforced thermoplastic composite material. Background Technology

[0002] Glass fiber is a high-performance inorganic non-metallic material. Glass fiber reinforced thermoplastic composites improve the shortcomings of thermoplastic resins in terms of strength, hardness, and heat resistance, and have excellent comprehensive performance. They are widely used in building materials, electronics, aerospace, automobiles and rail transportation.

[0003] As people become increasingly aware of material safety, there are strict requirements for the flame retardant properties of materials. However, several commonly used thermoplastic resins are flammable or combustible materials. To meet the relevant regulations and achieve the corresponding flame retardant rating, a certain amount of flame retardant is usually added during the granulation process. However, the addition of glass fiber, due to its shape characteristics and physical properties causing the "wick effect," deteriorates the flame retardant properties of the composite material. To meet the flame retardant requirements, more flame retardant needs to be added to the composite material during the production of glass fiber reinforced thermoplastic composites, leading to increased production costs and reduced performance.

[0004] The publication number CN117700836A discloses a method for preparing flame-retardant glass fiber and a thermoplastic resin composite material. The flame-retardant glass fiber includes glass fiber and a coating layer covering the surface of the glass fiber. The coating layer includes a phosphorus-silane coupling agent, but its flame-retardant performance still needs to be improved. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a flame-retardant glass fiber with high flame-retardant properties, its preparation method and fiber-reinforced thermoplastic composite material.

[0006] This invention provides a flame-retardant glass fiber, comprising: glass fiber and a flame-retardant coating attached to the surface of the glass fiber; the flame-retardant coating comprises a flame retardant, an aminosilane coupling agent, and a film-forming agent;

[0007] The flame retardant is selected from complexes formed by phosphonates and iron ions and / or complexes formed by grafted phosphorous acid resins and iron ions.

[0008] The mass of the flame retardant is 0.5% to 20% of the mass of the flame retardant coating;

[0009] The mass of the aminosilane coupling agent is 0.5% to 20% of the mass of the flame-retardant coating;

[0010] The mass of the film-forming agent is 60% to 99% of the mass of the flame-retardant coating.

[0011] Preferably, the iron ion content in the flame retardant is 1-3 wt%.

[0012] The phosphonic acid compound is selected from one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, and hydroxyethylidene diphosphonic acid;

[0013] The resin used for grafting phosphorous acid is selected from polyethyleneimine grafted with phosphorous acid.

[0014] Preferably, the molecular weight of the polyethyleneimine in the grafted phosphorous acid polyethyleneimine is 300-600 g / mol;

[0015] And / or, the aminosilane coupling agent is selected from γ-aminopropyltriethoxysilane and / or γ-aminoethylaminopropyltrimethoxysilane;

[0016] And / or, the film-forming agent is selected from polyurethane film-forming agents and / or epoxy film-forming agents;

[0017] And / or, the flame-retardant coating further includes an additive; the additive is present in an amount of 0.1% to 8% of the mass of the flame-retardant coating.

[0018] Preferably, the complex formed by the phosphonium compound and iron ions is prepared by the following method: mixing an aqueous solution of the phosphonium compound with an iron salt solution, and then adjusting the pH of the system to neutral to obtain a solution containing the complex formed by the phosphonium compound and iron ions;

[0019] The complex formed by the grafted phosphorous acid resin and iron ions is prepared by the following method: the resin solution is mixed with the phosphorous acid solution, then formaldehyde solution is added and mixed, then iron salt solution is added and mixed, and finally the pH value of the system is adjusted to neutral to obtain a solution containing the complex formed by the grafted phosphorous acid resin and iron ions.

[0020] Preferably, the film-forming agent is selected from polyurethane film-forming agents and epoxy film-forming agents; the mass ratio of the polyurethane film-forming agent to the epoxy film-forming agent is (1-5):5;

[0021] And / or, the polyurethane film-forming agent is selected from polyester-type polyurethane film-forming agents; the epoxy film-forming agent is selected from modified epoxy film-forming agents;

[0022] And / or, the epoxy film-forming agent has an epoxy equivalent of 200 to 500;

[0023] And / or, the additives are selected from wetting agents and / or lubricants.

[0024] Preferably, the mass of the flame-retardant coating is 1% to 3% of the mass of the flame-retardant glass fiber.

[0025] The present invention also provides a method for preparing the above-mentioned flame-retardant glass fiber, comprising the following steps:

[0026] S1) The hydrolyzed aminosilane coupling agent, film-forming agent solution and flame retardant are mixed in water to obtain an impregnating agent;

[0027] S2) The wetting agent is coated onto the surface of the glass fiber and dried to obtain flame-retardant glass fiber. Preferably, the film-forming agent solution is selected from polyurethane film-forming agent solution and / or epoxy film-forming agent solution;

[0028] The solid content of the polyurethane film-forming agent solution is preferably 48% to 50%;

[0029] The viscosity of the polyurethane film-forming agent solution is 100–1000 mPa·s;

[0030] The particle size of the polyurethane film-forming agent solution is 200–500 nm;

[0031] The solid content of the epoxy film-forming agent solution is 58% to 62%;

[0032] The viscosity of the epoxy film-forming agent solution is 100–3000 mPa·s;

[0033] The epoxy film-forming agent solution has a particle size of 200–1400 nm.

[0034] Preferably, the solid content of the wetting agent is 5% to 20%;

[0035] The moisture content of the flame-retardant glass fiber is less than 0.05%;

[0036] The coating method in step S2) is roller coating; the linear speed of the roller coating is 10-20 m / min.

[0037] The present invention also provides a fiber-reinforced thermoplastic composite material comprising the above-mentioned flame-retardant glass fiber and thermoplastic resin.

[0038] Compared with existing technologies, the flame-retardant glass fiber provided by this invention utilizes the large specific surface area of ​​glass fiber to load a flame-retardant coating with a highly efficient flame retardant that rapidly catalyzes char formation. This results in a synergistic flame-retardant effect. When used in the preparation of fiber-reinforced thermoplastic composites, it promotes the addition of flame retardants to the matrix at the interface between the flame-retardant glass fiber and the resin matrix, achieving a synergistic flame-retardant effect. This improves the quality and efficiency of char formation, suppresses the wicking effect of the fiber, and enhances flame-retardant performance. It can also reduce the amount of externally added flame retardant used in the granulation process, lowering production costs while improving mechanical properties, thus showing broad application prospects in actual industrial production.

[0039] The test results show that the composite material prepared by flame-retardant glass fiber achieves UL94 V0 flame retardant performance with a 20% reduction in the amount of added flame retardant, and the overall mechanical properties can be improved by 5% to 10%, while the production cost of flame-retardant granules is reduced by about 10%. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] This invention provides a flame-retardant glass fiber, comprising: glass fiber and a flame-retardant coating attached to the surface of the glass fiber; the flame-retardant coating comprises a flame retardant, an aminosilane coupling agent, and a film-forming agent; the flame retardant is a complex formed by a phosphonite compound and iron ions and / or a complex formed by a resin grafted with phosphorous acid and iron ions; the mass of the flame retardant is 0.5% to 20% of the mass of the flame-retardant coating; the mass of the aminosilane coupling agent is 0.5% to 20% of the mass of the flame-retardant coating; and the mass of the film-forming agent is 60% to 99% of the mass of the flame-retardant coating.

[0042] In one specific embodiment of the present invention, the diameter of the glass fiber is preferably 8 to 20 micrometers; optionally, the diameter of the glass fiber is 8 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 17 micrometers, 20 micrometers or any two of the above values.

[0043] The present invention uses a complex containing phosphonic acid groups and iron ions as a flame retardant, wherein the content of iron ions in the flame retardant is preferably 1 to 3 wt%; optionally, the content of iron ions in the flame retardant is 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, or any two of the above values.

[0044] In one specific embodiment of the present invention, the flame retardant is a complex formed by a phosphonate compound and iron ions; the iron ion content in the flame retardant is preferably 1-3 wt%, more preferably 2 wt%.

[0045] In one specific embodiment of the present invention, the complex formed by the phosphonate compound and iron ions is prepared by the following method: an aqueous solution of the phosphonate compound is mixed with an iron salt solution, and then the pH of the system is adjusted to neutral to obtain a solution containing the complex formed by the phosphonate compound and iron ions.

[0046] In one specific embodiment of the present invention, the phosphonic acid compound is preferably one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, and hydroxyethylidene diphosphonic acid.

[0047] In one specific embodiment of the present invention, the iron salt can be any soluble iron salt known to those skilled in the art, and there are no special limitations. In the present invention, ferric nitrate is preferred.

[0048] In a specific embodiment of the present invention, the mass concentration of the phosphonium compound in the aqueous solution is preferably 10% to 30%; optionally, the mass concentration of the phosphonium compound in the aqueous solution is 10%, 15%, 20%, 25%, 30%, or any two of the above values; the mass concentration of the iron salt in the iron salt solution is preferably 10% to 30%; optionally, the mass concentration of the iron salt in the iron salt solution is 10%, 15%, 20%, 25%, 30%, or any two of the above values; the volume ratio of the aqueous solution of the phosphonium compound to the iron salt solution is preferably 100:(0.5 to 3); optionally, the volume ratio of the aqueous solution of the phosphonium compound to the iron salt solution is 100:0.5, 100:1, 100:2, 100:3, or any two of the above ratios.

[0049] In a specific embodiment of the present invention, the mass concentration of the phosphonate compound in the aqueous solution is preferably 20%; the mass concentration of the iron salt in the iron salt solution is preferably 20%; and the volume ratio of the aqueous solution of the phosphonate compound to the iron salt solution is preferably 100:1.

[0050] In one specific embodiment of the present invention, it is preferable to slowly add the iron salt solution to the aqueous solution of the phosphonate compound for mixing.

[0051] In a specific embodiment of the present invention, the preferred mixing temperature of the aqueous solution of the phosphonium compound and the iron salt solution is 70°C to 90°C; optionally, the mixing temperature of the aqueous solution of the phosphonium compound and the iron salt solution is 70°C, 75°C, 80°C, 85°C, 90°C or any two of the above values; the preferred mixing time is 1 to 3 hours; optionally, the mixing time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours or any two of the above values.

[0052] In a specific embodiment of the present invention, the preferred temperature for mixing the aqueous solution of the phosphonic acid compound with the iron salt solution is 80°C; the preferred mixing time is 2 hours.

[0053] In one specific embodiment of the present invention, it is preferred to use ammonia water to adjust the pH value of the system to neutral.

[0054] In one specific embodiment of the present invention, the solid content of the solution containing the complex formed by the phosphonite compound and iron ions is preferably 20% to 50%; optionally, the solid content of the solution containing the complex formed by the phosphonite compound and iron ions is 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two of the above values.

[0055] In one specific embodiment of the present invention, the solid content of the solution containing the complex formed by the phosphonate compound and iron ions is preferably 35%.

[0056] In one specific embodiment of the present invention, the flame retardant is a complex formed by grafted phosphorous acid resin and iron ions, and the content of iron ions in the flame retardant is preferably 2-3 wt%, more preferably 2.5 wt%.

[0057] In one specific embodiment of the present invention, the resin for grafting phosphorous acid is selected from polyethyleneimine grafted with phosphorous acid; the molecular weight of the polyethyleneimine grafted with phosphorous acid is preferably 300-600 g / mol.

[0058] In a specific embodiment of the present invention, the complex formed by the resin of the branched phosphorous acid and iron ions is prepared by the following method: the resin solution is mixed with the phosphorous acid solution, then formaldehyde solution is added and mixed, then iron salt solution is added and mixed, and finally the pH value of the system is adjusted to neutral to obtain a solution containing the complex formed by the resin of the branched phosphorous acid and iron ions.

[0059] In a specific embodiment of the present invention, the mass concentration of resin in the resin solution is preferably 5% to 20%; optionally, the mass concentration of resin in the resin solution is 5%, 10%, 15%, 20%, or any two of the above values; the mass concentration of phosphorous acid solution is preferably 10% to 40%; optionally, the mass concentration of phosphorous acid solution is 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any two of the above values; the volume ratio of resin solution to phosphorous acid solution is preferably (2-5):1; optionally, the volume ratio of resin solution to phosphorous acid solution is 2:1, 3:1, 4:1, 5:1, or any two of the above ratios; the mass concentration of formaldehyde in the formaldehyde solution is preferably 35% to 40%; optionally, the mass concentration of formaldehyde solution is 35%. The volume ratio of the resin solution to the formaldehyde solution is preferably (15-20):1; optionally, the volume ratio of the resin solution to the formaldehyde solution is 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, or any two of the above ratios; the mass concentration of the iron salt in the iron salt solution is preferably 10%-30%; optionally, the mass concentration of the iron salt in the iron salt solution is 10%, 15%, 20%, 25%, 30%, or any two of the above values; the volume ratio of the resin solution to the iron salt solution is preferably (30-50):1; optionally, the volume ratio of the resin solution to the iron salt solution is 30:1, 35:1, 40:1, 45:1, 50:1, or any two of the above ratios.

[0060] In a specific embodiment of the present invention, the resin concentration in the resin solution is preferably 7% to 10%; the phosphorous acid solution is preferably 20%; the volume ratio of the resin solution to the phosphorous acid solution is preferably 3:1; the formaldehyde concentration in the formaldehyde solution is preferably 37%; the volume ratio of the resin solution to the formaldehyde solution is preferably 17:1; the iron salt concentration in the iron salt solution is preferably 20%; and the volume ratio of the resin solution to the iron salt solution is preferably 40:1.

[0061] In a specific embodiment of the present invention, the resin solution and the phosphorous acid solution are preferably mixed at room temperature; the mixing time of the resin solution and the phosphorous acid solution is preferably 30-90 min, more preferably 50-80 min, and even more preferably 60 min; the mixing speed of the resin solution and the phosphorous acid solution is preferably 500-1000 rpm, more preferably 600-900 rpm, and even more preferably 800 rpm; the mixing temperature of the formaldehyde solution is preferably 100℃-120℃, more preferably 110℃; and the mixing time of the formaldehyde solution is preferably 2-6 h, more preferably 3-6 h. The mixing time for adding formaldehyde solution is preferably 1000-1500 rpm, more preferably 1100-1400 rpm, and even more preferably 1200 rpm; the mixing temperature for adding iron salt solution is preferably 70℃-90℃, more preferably 75℃-85℃, and even more preferably 80℃; the mixing time for adding iron salt solution is preferably 1-3 hours, more preferably 1.5-2.5 hours, and even more preferably 2 hours; the mixing speed for adding iron salt solution is preferably 1000-1500 rpm, more preferably 1100-1400 rpm, and even more preferably 1200 rpm.

[0062] In one specific embodiment of the present invention, it is preferred to use ammonia water to adjust the pH value of the system to neutral.

[0063] In one specific embodiment of the present invention, the solid content of the solution containing the resin containing the branched phosphorous acid and the complex formed by iron ions is preferably 20% to 50%; optionally, the solid content of the solution containing the resin containing the branched phosphorous acid and the complex formed by iron ions is 20%, 25%, 30%, 35%, 40%, 45%, 50% or any two of the above values.

[0064] In one specific embodiment of the present invention, the solid content of the solution containing the resin containing phosphite and the complex formed by iron ions is preferably 35%.

[0065] In one specific embodiment of the present invention, optionally, the mass of the flame retardant is 0.5%, 1%, 3%, 5%, 8%, 10%, 11%, 13%, 15%, 18%, 20% of the mass of the flame retardant coating, or a range between any two of the above values.

[0066] Adding an aminosilane coupling agent to a flame-retardant coating can increase the nitrogen content in the coating and improve the compatibility of the components. In a specific embodiment of the present invention, the aminosilane coupling agent is preferably γ-aminopropyltriethoxysilane and / or γ-aminoethylaminopropyltrimethoxysilane.

[0067] In one specific embodiment of the present invention, optionally, the mass of the aminosilane coupling agent is 0.5%, 1%, 3%, 5%, 8%, 10%, 11%, 13%, 15%, 18%, 20% of the mass of the flame-retardant coating, or a range between any two of the above values.

[0068] In a specific embodiment of the present invention, the film-forming agent is preferably a polyurethane film-forming agent and / or an epoxy film-forming agent, more preferably a polyurethane film-forming agent and an epoxy film-forming agent; the polyurethane film-forming agent is a polyester-type polyurethane film-forming agent; specifically, the polyurethane film-forming agent may be VONDIC1672NE; the epoxy film-forming agent is preferably a modified epoxy resin film-forming agent; the epoxy equivalent of the epoxy film-forming agent is preferably 200-500; optionally, the epoxy equivalent of the epoxy film-forming agent is... The oxygen equivalent is 200, 300, 400, 500, or any two of the above values; specifically, the epoxy film-forming agent can be bisphenol A type epoxy resin, and more specifically, it can be E-51 type epoxy resin; the mass ratio of the polyurethane film-forming agent to the epoxy film-forming agent is preferably (1-5):5; optionally, the mass ratio of the polyurethane film-forming agent to the epoxy film-forming agent is 1:5, 1.5:5, 2:5, 3:5, 4:5, 5:5, or any two of the above values.

[0069] In one specific embodiment of the present invention, optionally, the mass of the film-forming agent is 60%, 62%, 64%, 65%, 66%, 68%, 70%, 72%, 74%, 75%, 76%, 78%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, 99% of the mass of the flame-retardant coating, or a range between any two of the above values.

[0070] In one specific embodiment of the present invention, the flame-retardant coating preferably further includes an additive; the mass of the additive is preferably 0.1% to 8% of the mass of the flame-retardant coating; optionally, the mass of the additive is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% of the mass of the flame-retardant coating or a range between any two of the above values.

[0071] In this invention, the additives are those well known to those skilled in the art that can improve certain properties of the coating, such as uniformity. A specific preferred embodiment provided by this invention includes wetting agents and / or lubricants. The wetting agent can be any wetting agent well known to those skilled in the art, and there are no special limitations. In this invention, silicone wetting agents are preferred, and BYK-P9920 is more preferred. The lubricant can be any water-based organosilicon lubricant well known to those skilled in the art, and there are no special limitations. In this invention, BYK-024 is preferred.

[0072] In one specific embodiment of the present invention, the mass of the flame-retardant coating is preferably 1% to 3% of the mass of the flame-retardant glass fiber; optionally, the mass of the flame-retardant coating is 1%, 1.5%, 2%, 2.5%, 3% of the mass of the flame-retardant glass fiber or a range between any two of the above values.

[0073] The flame-retardant glass fiber provided by this invention utilizes the large specific surface area of ​​glass fiber to load a flame-retardant coating with a highly efficient flame retardant that rapidly catalyzes char formation. This coating exhibits a synergistic flame-retardant function. When used in the preparation of fiber-reinforced thermoplastic composites, it promotes the char formation of the externally added flame retardant at the interface between the flame-retardant glass fiber and the resin matrix, achieving a synergistic flame-retardant effect. This improves the quality and efficiency of char formation, suppresses the wicking effect of the fiber, and enhances flame-retardant performance. It can reduce the amount of externally added flame retardant used in the granulation process, lowering production costs while also improving mechanical properties, thus showing broad application prospects in actual industrial production.

[0074] The present invention also provides a method for preparing the above-mentioned flame-retardant glass fiber, comprising the following steps: S1) mixing the hydrolyzed aminosilane coupling agent, film-forming agent solution and flame retardant in water to obtain an impregnation agent; S2) coating the impregnation agent on the surface of the glass fiber and drying it to obtain flame-retardant glass fiber.

[0075] In this invention, there are no special restrictions on the source of any raw materials; commercially available materials are acceptable. The aminosilane coupling agent, film-forming agent, and flame retardant are all as described above and will not be repeated here.

[0076] In one specific embodiment of the present invention, the film-forming agent solution is preferably a polyurethane film-forming agent solution and / or an epoxy film-forming agent solution.

[0077] In one specific embodiment of the present invention, the solid content of the polyurethane film-forming agent solution is preferably 48% to 50%; optionally, the solid content of the polyurethane film-forming agent solution is 48%, 49%, 50% or any two of the above values.

[0078] In one specific embodiment of the present invention, the viscosity of the polyurethane film-forming agent solution is preferably 100–1000 mPa·s. In another specific embodiment of the present invention, the particle size of the polyurethane film-forming agent solution is preferably 200–500 nm.

[0079] In one specific embodiment of the present invention, the solid content of the epoxy film-forming agent solution is preferably 58% to 62%; optionally, the solid content of the epoxy film-forming agent solution is 58%, 59%, 60%, 61%, 62% or any two of the above values.

[0080] In one specific embodiment of the present invention, the viscosity of the epoxy film-forming agent solution is preferably 100-3000 mPa·s.

[0081] In one specific embodiment of the present invention, the particle size of the epoxy film-forming agent solution is preferably 200-1400 nm.

[0082] The hydrolyzed aminosilane coupling agent, film-forming agent solution, and flame retardant are mixed in water to obtain an impregnating aqueous agent. In this invention, the specific steps are as follows: the aminosilane coupling agent is first hydrolyzed until it is clear and transparent with no oil film on the surface, and then mixed with other components. The mixing method can be any method known to those skilled in the art and is not particularly limited. The solid content of the impregnating aqueous agent is preferably 5% to 20%. Optionally, the solid content of the impregnating aqueous agent is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any two of the above values.

[0083] The wetting agent is coated onto the surface of the glass fiber. The coating method can be any method known to those skilled in the art and is not particularly limited. In this invention, roller coating is preferred. The linear speed of the roller coating is preferably 10 to 20 m / min. Optionally, the linear speed of the roller coating is 10 m / min, 11 m / min, 12 m / min, 13 m / min, 14 m / min, 15 m / min, 16 m / min, 17 m / min, 18 m / min, 19 m / min, 20 m / min or any two of the above values.

[0084] After coating, the fibers are preferably chopped and then dried to obtain flame-retardant glass fibers. The length of the chopped fibers is preferably 2-5 mm; optionally, the length of the chopped fibers is 2 mm, 3 mm, 4 mm, 5 mm, or any two of the above values. The drying temperature is preferably 150℃-200℃; optionally, the drying temperature is 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any two of the above values. The drying time is preferably 5-10 min; optionally, the drying time is 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any two of the above values. The moisture content of the flame-retardant glass fibers is preferably less than 0.05%.

[0085] The method for preparing flame-retardant glass fiber provided by this invention is simple, the production process is easy to control, and it is suitable for large-scale production. The resulting flame-retardant glass fiber is halogen-free and meets environmental standards. When used to reinforce thermoplastic resins, it exhibits excellent flame-retardant effects and mechanical properties, demonstrating great application potential in the industrial field.

[0086] The present invention also provides a fiber-reinforced thermoplastic composite material comprising the aforementioned flame-retardant glass fiber and thermoplastic resin. The flame-retardant coating of the flame-retardant glass fiber primarily functions to provide highly efficient catalytic char formation flame retardancy, protect the glass fiber from bundle formation, and improve the compatibility of the glass fiber-resin interface.

[0087] In one specific embodiment of the present invention, the mass of the flame-retardant glass fiber is preferably 10% to 40% of the mass of the fiber-reinforced thermoplastic composite material; optionally, the mass of the flame-retardant glass fiber is 10%, 15%, 20%, 25%, 30%, 35%, 40% of the mass of the fiber-reinforced thermoplastic composite material or a range between any two of the above values.

[0088] In one specific embodiment of the present invention, the thermoplastic resin may be any thermoplastic resin known to those skilled in the art, and there are no special limitations, including but not limited to PBT resin and / or PA resin.

[0089] In a specific embodiment of the present invention, the fiber-reinforced thermoplastic composite material preferably further includes an external flame retardant; the mass of the external flame retardant is preferably 5% to 20% of the fiber-reinforced thermoplastic composite material; optionally, the mass of the external flame retardant is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% of the fiber-reinforced thermoplastic composite material or any two of the above values; the type of the external flame retardant is preferably an organic aluminum phosphonate flame retardant; in the embodiments provided by the present invention, Clariant Exolit OP1240 is specifically used as an example for illustration.

[0090] In a specific embodiment of the present invention, the fiber-reinforced thermoplastic composite material preferably further includes an additive; the mass of the additive is preferably 0.1% to 5% of the fiber-reinforced thermoplastic composite material; optionally, the mass of the added flame retardant is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% of the fiber-reinforced thermoplastic composite material or any two of the above values; the additive is preferably an antioxidant; the type of antioxidant is preferably a hindered phenolic antioxidant.

[0091] In one specific embodiment of the present invention, the fiber-reinforced thermoplastic composite material is preferably obtained by extrusion granulation; the temperature of the extrusion granulation can be selected according to the type of thermoplastic resin, specifically 220℃~250℃.

[0092] To further illustrate the present invention, the following detailed description of a flame-retardant glass fiber, its preparation method, and fiber-reinforced thermoplastic composite material provided by the present invention is provided in conjunction with embodiments.

[0093] All reagents used in the following examples are commercially available; the molecular weight of PEI used in the examples is 300-600 g / mol.

[0094] Preparation of PEIP-Fe: First, PEI was dissolved in deionized water and stirred until homogeneous to obtain 300 mL of PEI solution with a concentration of 7 wt%. Then, under stirring conditions of 800 rpm, 100 mL of 20 wt% phosphorous acid solution was slowly added to the flask and stirred until homogeneous. Next, 20 g of 37% formaldehyde solution was slowly added, and the mixture was rapidly stirred at 110 °C for 4 h to achieve homogeneity. Finally, 1.55 g of 20 wt% ferric nitrate solution was slowly added, and the mixture was stirred for 2 h. Finally, the pH was adjusted to approximately 7 with ammonia water to obtain the PEIP-Fe solution.

[0095] Preparation of ATMP-Fe: First, ATMP was dissolved in deionized water and stirred until homogeneous to obtain a 20wt% ATMP solution. Then, 2g of a 20wt% ferric nitrate solution was slowly added dropwise to 200mL of the ATMP solution. The mixture was heated at 80℃ and stirred for 2 hours until completely dissolved. Finally, the pH was adjusted to approximately 7 with ammonia to obtain the ATMP-Fe solution.

[0096] Example 1

[0097] S1) Preparation of the wetting agent aqueous solution:

[0098] A certain amount of coupling agent, film-forming agent, high-efficiency catalytic flame retardant, and other additives are weighed according to the formula, diluted with water in sequence, and added to prepare an impregnation aqueous solution. The coupling agent is A1100 (γ-aminopropyltriethoxysilane coupling agent), which needs to be hydrolyzed until clear and transparent with no oil film on the surface. Its preferred proportion in the formula is 10% (based on dry weight). The film-forming agents used include two types of polyurethane film-forming agents (VONDIC). The formulation includes 1672NE and an epoxy film-forming agent (E-51 type), wherein the epoxy film-forming agent is preferably used in a 50% (dry weight) proportion, and the polyurethane film-forming agent is preferably used in a 30% (dry weight) proportion; the high-efficiency flame-retardant catalyst is PEIP-Fe, with a solid content preferably of 35%, and its proportion in the formulation is preferably 5% (dry weight); the auxiliary agent used is wetting agent BYK-P9920, with a proportion in the formulation preferably of 5% (dry weight); the total solid content of the impregnation water is 10%.

[0099] S2) Preparation of flame-retardant glass fiber:

[0100] A wetting agent is uniformly coated onto the surface of glass fiber precursor by roller coating. The glass fiber precursor is then chopped and dried to remove surface moisture, resulting in a flame-retardant glass fiber product. The roller coating linear speed is 16 m / min, the preferred drying temperature is 190℃, the chopped length is 4.5 mm, the diameter is 10–11 micrometers, and the drying time is 7 min. The dry matter content of the wetting agent coated on the surface of the dried glass fiber precursor is 1%–2% (as shown in Table 1), and the moisture content of the resulting flame-retardant glass fiber product is less than 0.05%.

[0101] S3) Preparation of flame-retardant glass fiber reinforced PBT resin composites:

[0102] The prepared flame-retardant glass fiber was granulated by twin-screw extrusion with PBT resin (BASF, B4520) and flame retardant (Exolit OP1240). The granulation formula is as follows: PBT resin content is 53.7-57.7 wt% (total 100%), flame-retardant glass fiber content is 30 wt%, the content of added flame retardant is shown in Table 1, and the content of antioxidant (1010) is 0.3%. The required proportions of resin, flame retardant, and additives were accurately weighed and mixed in a high-speed mixer for 3 minutes. The flame-retardant glass fiber and the mixed material were then extruded and granulated by twin-screw extrusion at a processing temperature of 220℃-250℃. After granulation, the granules were annealed and dried in an oven. Then, standard specimens were injection molded according to standards, and flame retardant performance and mechanical properties were tested according to relevant standards. The results are shown in Table 1.

[0103] Example 2

[0104] The difference from Example 1 is that the polyurethane film-forming agent accounts for 25% (by dry weight) in the formulation, and the high-efficiency flame retardant catalyst PEIP-Fe accounts for 10% (by dry weight) in the formulation.

[0105] Example 3

[0106] The difference from Example 1 is the high-efficiency flame retardant catalyst PEIP-Fe, in which the polyurethane film-forming agent accounts for 20% (by dry weight) in the formulation, and PEIP-Fe accounts for 15% (by dry weight) in the formulation.

[0107] Example 4

[0108] The difference from Example 1 is the high-efficiency flame retardant catalyst PEIP-Fe, in which the polyurethane film-forming agent accounts for 15% (by dry weight) in the formulation, and PEIP-Fe accounts for 20% (by dry weight) in the formulation.

[0109] Example 5

[0110] The difference from Example 1 is that the high-efficiency flame retardant catalyst is ATMP-Fe, which accounts for 5% of the formulation (based on dry weight).

[0111] Example 6

[0112] The difference from Example 2 is that the high-efficiency flame retardant catalyst is ATMP-Fe, which accounts for 10% of the formulation (based on dry weight).

[0113] Example 7

[0114] The difference from Example 3 is that the high-efficiency flame retardant catalyst is ATMP-Fe, which accounts for 15% of the formulation (based on dry weight).

[0115] Example 8

[0116] The difference from Example 4 is that the high-efficiency flame retardant catalyst is ATMP-Fe, which accounts for 20% of the formulation (based on dry weight).

[0117] Comparative Example 1

[0118] Fiber-reinforced PBT resin composites were prepared using commercially available chopped glass fiber products for reinforcing PBT resin (CPIC, ECS303-4.5-H / ECT) according to the method in Example 1.

[0119] Comparative Example 2

[0120] The difference from Example 1 is that no highly efficient catalytic flame retardant was added; it is a blank control sample.

[0121] The following standards are used for testing: tensile strength test standard GB / T 1040.1-2018; bending strength test standard GB / T9341-2008; and cantilever beam impact strength test standard GB / T1843-2008.

[0122] Flame retardant performance testing: The test is conducted according to the industry-standard UL94 flame retardant test. Flame retardant test strips are prepared by injection molding, requiring a smooth surface, no burrs, and uniform density. Strip dimensions: (125±5)×(13.0±0.5)×thickness (0.8mm, 1.6mm). At least two sets of samples are required, with 5 samples in each set. The test is conducted according to the UL94 flame retardant performance test method. After burning for 10±0.5 seconds, the afterflame time t1 is recorded. Immediately after the afterflame stops, it is reignited for 10±0.5 seconds. After removal, the afterflame time t2 and afterburn time t3 are recorded. It is also recorded whether the strip is completely burned and whether any dripping material ignites the cotton during the test. Flame retardant performance assessment: V-0 grade: for a single sample, t1 / t2 ≤ 10s; for all samples, t1 + t2 ≤ 50s; for a single sample, t2 + t3 ≤ 30s; does not burn completely and does not ignite cotton; V-1 grade: for a single sample, t1 / t2 ≤ 30s; for all samples, t1 + t2 ≤ 250s; for a single sample, t2 + t3 ≤ 60s; does not burn completely and does not ignite cotton; V-2 grade: for a single sample, t1 / t2 ≤ 30s; for all samples, t1 + t2 ≤ 250s; for a single sample, t2 + t3 ≤ 60s; does not burn completely and ignites cotton.

[0123] Table 1 Performance test results of fiber-reinforced PBT resin composites

[0124]

[0125]

[0126] The test results above show that the flame-retardant glass fiber reinforced PBT composite material prepared using the method provided in this application exhibits superior flame-retardant and mechanical properties compared to Comparative Examples 1 and 2. When adding the same 12wt% flame retardant, a V0 rating of 0.8mm can be achieved with PEIP-Fe as the catalytic flame retardant at a dosage of 15%. A V0 rating of 0.8mm can also be achieved with ATMP-Fe as the catalytic flame retardant at a dosage of 20%. In contrast, commercially available chopped strand products for reinforced PBT resin require 16wt% flame retardant to achieve V0, indicating a reduction of over 20wt% in flame retardant usage. This demonstrates that the flame-retardant coating containing the catalytic flame retardant provided by this invention has a significant effect on improving flame-retardant performance, with PEIP-Fe showing better flame-retardant performance. Regarding mechanical properties, the mechanical properties of ATMP-Fe as the catalytic flame retardant are superior to both the comparative and PEIP-Fe samples, indicating that the interfacial compatibility of PEIP-Fe is worse than that of ATMP-Fe. Based on the above analysis, Examples 3 and 8 show the best flame retardant performance, with Example 8 exhibiting superior overall mechanical properties.

[0127] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flame retardant glass fiber, characterized in that, include: Glass fiber and a flame-retardant coating attached to the surface of the glass fiber; the flame-retardant coating includes a flame retardant, an aminosilane coupling agent, and a film-forming agent; The flame retardant is selected from complexes formed by phosphonates and iron ions and / or complexes formed by grafted phosphorous acid resins and iron ions. The flame retardant accounts for 0.5% to 20% of the mass of the flame retardant coating. The mass of the aminosilane coupling agent is 0.5% to 20% of the mass of the flame-retardant coating; The mass of the film-forming agent is 60% to 99% of the mass of the flame-retardant coating; The iron ion content in the flame retardant is 1~3 wt%; The phosphonic acid compound is selected from one or more of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, and hydroxyethylidene diphosphonic acid; The resin used for grafting phosphorous acid is selected from polyethyleneimine grafted with phosphorous acid; The molecular weight of the polyethyleneimine in the grafted phosphorous acid polyethyleneimine is 300~600 g / mol; The mass of the flame-retardant coating is 1% to 3% of the mass of the flame-retardant glass fiber.

2. The flame-retardant glass fiber according to claim 1, characterized in that, The aminosilane coupling agent is selected from γ-aminopropyltriethoxysilane and / or γ-aminoethylaminopropyltrimethoxysilane; And / or, the film-forming agent is selected from polyurethane film-forming agents and / or epoxy film-forming agents; And / or, the flame-retardant coating further includes an additive; the mass of the additive is 0.1% to 8% of the mass of the flame-retardant coating.

3. The flame retardant glass fiber of claim 2, wherein, The complex formed by the phosphonium compound and iron ions is prepared by the following method: an aqueous solution of the phosphonium compound is mixed with an iron salt solution, and then the pH of the system is adjusted to neutral to obtain a solution containing the complex formed by the phosphonium compound and iron ions. The complex formed by the grafted phosphorous acid resin and iron ions is prepared by the following method: the resin solution is mixed with the phosphorous acid solution, then formaldehyde solution is added and mixed, then iron salt solution is added and mixed, and finally the pH value of the system is adjusted to neutral to obtain a solution containing the complex formed by the grafted phosphorous acid resin and iron ions.

4. The flame retardant glass fiber of claim 3, wherein, The film-forming agent is selected from polyurethane film-forming agent and epoxy film-forming agent; the mass ratio of polyurethane film-forming agent to epoxy film-forming agent is (1~5):5; And / or, the polyurethane film-forming agent is selected from polyester-type polyurethane film-forming agents; the epoxy film-forming agent is selected from modified epoxy film-forming agents; And / or, the epoxy film-forming agent has an epoxy equivalent of 200~500; And / or, the additives are selected from wetting agents and / or lubricants.

5. A method for preparing flame-retardant glass fiber according to claim 1, characterized in that, Includes the following steps: S1) The hydrolyzed aminosilane coupling agent, film-forming agent solution and flame retardant are mixed in water to obtain an impregnating agent; S2) The wetting agent is coated onto the surface of the glass fiber and dried to obtain flame-retardant glass fiber.

6. The preparation method according to claim 5, characterized in that, The film-forming agent solution is selected from polyurethane film-forming agent solution and / or epoxy film-forming agent solution; The solid content of the polyurethane film-forming agent solution is 48%~50%; The viscosity of the polyurethane film-forming agent solution is 100~1000 mPa·s; The particle size of the polyurethane film-forming agent solution is 200~500 nm; The solid content of the epoxy film-forming agent solution is 58%~62%; The viscosity of the epoxy film-forming agent solution is 100~3000 mPa·s; The epoxy film-forming agent solution has a particle size of 200~1400 nm.

7. The preparation method according to claim 5, characterized in that, The solid content of the impregnating agent is 5% to 20%; The moisture content of the flame-retardant glass fiber is less than 0.05%; The coating method in step S2) is roller coating; the linear speed of the roller coating is 10~20 m / min.

8. A fiber-reinforced thermoplastic composite material, characterized in that, It includes flame-retardant glass fiber as described in any one of claims 1 to 4 or flame-retardant glass fiber prepared by the preparation method described in any one of claims 5 to 7 and thermoplastic resin.

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