Preparation method of flame-retardant pre-oxidized fiber, flame-retardant pre-oxidized fiber and application

Abstract

The invention discloses a preparation method of a flame-retardant pre-oxidized fiber, the flame-retardant pre-oxidized fiber and application of the flame-retardant pre-oxidized fiber. The preparation method of the flame-retardant pre-oxidized fiber comprises the steps of unwinding, humidifying, drying and pre-oxidizing protofilaments. The pre-oxidation is carried out by adopting a gradient heating mode, and the tension in the fiber feeding process is controlled to be constant during the pre-oxidation. According to the method disclosed by the invention, processes such as a pre-oxidation process and protofilament releasing are improved, and the flame-retardant fiber with better performance is prepared. Compared with common fibers, the flame-retardant fiber disclosed by the invention has the advantages that the flammability is obviously reduced, the combustion rate is obviously reduced in the combustion process, the flame-retardant fiber can be quickly self-extinguished after leaving a fire source, less toxic smoke is released, and the flame-retardant fiber can be applied to clothes, home furnishing, decoration, non-woven fabrics and the like. The flame-retardant fiber provided by the invention can solve the problems of low limit oxygen index and environmental unfriendliness of the existing flame-retardant fiber, and can effectively improve the performance of the flame-retardant fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardant preoxidized fiber preparation, and further relates to a preparation method of the flame retardant preoxidized fiber and the flame retardant preoxidized fiber and its application. Background Art

[0002] Polyacrylonitrile pre-oxidized fiber, also known as PAN pre-oxidized fiber, is extremely flame-retardant, with a limiting oxygen index exceeding 45%. Its high-temperature resistance surpasses that of common flame-retardant fibers such as Kevlar, Nomex, and aramid. Pre-oxidized fiber maintains stable performance at 300°C, and its strength retention reaches 65% after 10 minutes at 500°C. It exhibits excellent thermal stability, and during combustion, the fiber does not melt, soften, or shrink, and there are no droplets (which will not burn the body), making it a quasi-non-combustible product. It also provides excellent thermal insulation and resistance to acid and alkali corrosion, chemical environments, and radiation. It possesses suitable textile processing properties, resulting in a lightweight, soft, and highly absorbent fabric with excellent post-processing and wearability. It can be used in both pure and blended textiles, as well as various industrial products.

[0003] Currently, phosphorus-based flame-retardant fibers and textiles are experiencing a positive overall development momentum, but phosphorus-containing compounds can also have adverse effects on the environment and the human body. Bromine-based flame-retardant fibers have been phased out globally, but phosphorus-based flame retardants are still widely used due to their excellent flame-retardant effects, and their production and usage are still growing. Studies have found that in many countries and regions, including Europe, Japan, and China, there are certain levels of phosphorus-containing flame retardant residues in the atmosphere, water, soil, human body, and some biological environmental media. Metabolites of phosphorus-containing flame retardants have even been detected in the urine and blood of some Germans. Therefore, accelerating the development of environmentally friendly flame-retardant fibers and flame retardants has become an important issue that needs to be urgently addressed globally. Summary of the Invention

[0004] In order to solve the problems arising in the prior art, the present invention proposes a method for preparing flame-retardant pre-oxidized fibers, flame-retardant pre-oxidized fibers and applications. The method of the present invention improves the pre-oxidation process and the process of releasing raw silk, and prepares flame-retardant fibers with better performance. Compared with ordinary fibers, the flame-retardant fibers of the present invention have significantly lower flammability, a significantly slower burning rate during the combustion process, can quickly self-extinguish after leaving the fire source, and release less toxic smoke, and can be used in clothing, home furnishings, decorations and non-woven fabrics, etc. The flame-retardant fibers of the present invention can solve the problems of low limiting oxygen index and environmental unfriendliness of existing flame-retardant fibers, and can effectively improve the performance of flame-retardant fibers.

[0005] One of the purposes of the present invention is to provide a method for preparing flame-retardant preoxidized fiber, comprising the steps of unwinding raw silk and preoxidizing it; the preoxidation is carried out in a gradient heating manner, and the tension of the fiber during the preoxidation process is controlled to be constant.

[0006] In the technical solution of the present invention, constant tension control is adopted in the fiber pre-oxidation process, and the rotation speed of the three- to seven-roller machine is controlled by online tension regulation to keep the tension constant during the fiber feeding process.

[0007] In the technical solution of the present invention, the method for preparing the flame-retardant preoxidized fiber may further include conventional steps for preparing preoxidized fibers in the art, and those skilled in the art may make corresponding adjustments based on production requirements.

[0008] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0009] The precursor comprises polyacrylonitrile precursor; and / or,

[0010] The step of releasing the wire adopts an active wire releasing method;

[0011] Preferably, when unwinding, the tension of the raw yarn is controlled to be 200 to 2000 cN;

[0012] More preferably,

[0013] The tension of the 3k-12k raw yarn is controlled to be 200-800cN; for example, 200, 300, 400, 500, 600, 700, 800cN, or a range consisting of any two of the above values; and / or,

[0014] The tension of the 12k-48k raw yarn is controlled to be 800-1200cN; for example, 800, 900, 1000, 1100, 1200cN, or a range consisting of any two of the above values; and / or,

[0015] The tension of the raw yarn above 48K is controlled to be 1200-2000 cN, for example, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000 cN and a range consisting of any two of the above values.

[0016] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0017] The steps of humidification and drying are also included between the steps of laying out the raw silk and pre-oxidation;

[0018] Preferably, the humidification step is to immerse the unwinding raw silk in water for 5-10 seconds at room temperature; and / or,

[0019] The drying temperature is 110-120° C., and / or the drying time is 10-15 seconds.

[0020] In the technical solution of the present invention, during drying, the fibers are dried by being passed along the blowing direction in a tubular heating furnace.

[0021] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0022] The atmosphere during the pre-oxidation is an air atmosphere; and / or,

[0023] The temperature gradient during the pre-oxidation process is not higher than 30°C, preferably the temperature gradient during the pre-oxidation process is not higher than 30°C, but not lower than 20°C; more preferably, the temperature gradient during the pre-oxidation process is 20-25°C; for example, 20, 21, 22, 23, 24, 25°C, and a range consisting of any two of the above values;

[0024] Preferably, the pre-oxidation process is carried out in a three-temperature zone gradient heating manner, which are respectively recorded as the first temperature zone, the second temperature zone and the third temperature zone, wherein the temperatures of the first temperature zone, the second temperature zone and the third temperature zone increase in sequence.

[0025] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0026] During the pre-oxidation process, the tension of the fiber is controlled to be constant at any value between 800 and 2000 cN during the fiber feeding process;

[0027] Preferably,

[0028] Controlling the fiber tension of 3k-12k to be constant at any value between 800 and 1200 cN; for example, 800, 900, 1000, 1100, 1200 cN and any value in the range consisting of any two of the above values; and / or,

[0029] Controlling the fiber tension of 12k-48k to be constant at any value between 1200 and 1600 cN; for example, 1200, 1300, 1400, 1500, 1600 cN and any value in the range of any two of the above values; and / or,

[0030] The fiber tension above 48K is controlled to be constant at any value between 1600 and 2000 cN, for example, 1600, 1700, 1800, 1900, 2000 cN and any value in the range consisting of any two of the above values.

[0031] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0032] In the pre-oxidation step,

[0033] The pre-oxidation temperature is 230-290°C, and the total pre-oxidation time is 45-75 minutes; preferably,

[0034] The starting temperature of the pre-oxidation is 230-250°C; preferably 235-245°C; for example, 230, 235, 240, 245, 250°C and a range consisting of any two of the above values; and / or,

[0035] The termination temperature of the pre-oxidation is 270-290°C; preferably 275-285°C; for example, 270, 275, 280, 285, 290°C and a range consisting of any two of the above values; and / or,

[0036] Preferably, the pre-oxidation is carried out in a gradient temperature increase manner, wherein the pre-oxidation treatment time in each temperature zone is the same; preferably, the pre-oxidation treatment time in each temperature zone is 15 to 25 minutes; for example, 15, 18, 20, 22, 25 minutes and a range consisting of any two of the above values.

[0037] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0038] The bulk density of the fiber during the pre-oxidation process is 1.23-1.48 g / cm 3 , and the bulk density of the fiber gradually increases during the pre-oxidation process;

[0039] Preferably, the fiber density after pre-oxidation in the first temperature zone is 1.23-1.28 g / cm 3 ; For example, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28 g / cm 3 and the range consisting of any two of the above values; and / or,

[0040] The fiber density after pre-oxidation in the second temperature zone is 1.32-1.38 g / cm 3 ; For example, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38 g / cm 3 and the range consisting of any two of the above values; and / or,

[0041] The fiber density after pre-oxidation in the third temperature zone is 1.42-1.48 g / cm 3 ; For example, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48 g / cm 3 and the range consisting of any two of the above values.

[0042] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0043] The oxygen content of the fiber during the pre-oxidation process is 6 to 12 wt%, and the oxygen content of the fiber gradually increases during the pre-oxidation process;

[0044] Preferably,

[0045] The oxygen content of the fiber after pre-oxidation in the first temperature zone is 6-8 wt%; preferably 6.3-8 wt%; for example, 6%, 6.3%, 7%, 8% and a range consisting of any two of the above values; and / or,

[0046] The oxygen content of the fiber after pre-oxidation in the second temperature zone is 8-10 wt %; preferably 8.5-10 wt %; for example, 8%, 8.5%, 9%, 10% and a range consisting of any two of the above values; and / or,

[0047] The oxygen content of the fiber after pre-oxidation in the third temperature zone is 10-12 wt %, preferably 10.5-12 wt %, such as 10%, 10.5%, 11%, 12% and a range consisting of any two of the above values.

[0048] In the technical solution of the present invention, the gradient temperature-raising oxidation furnace adopts three blast box oxidation furnaces connected in series, and three to seven rollers are used before and after the oxidation furnaces to transport materials.

[0049] In the method for preparing the flame-retardant preoxidized fiber of the present invention, preferably,

[0050] After pre-oxidation, the process further includes oiling and optionally collecting the fibers. In the oiling and collecting steps of the present invention, those skilled in the art can choose whether to perform the oiling and collecting steps based on subsequent use or transportation requirements.

[0051] A second object of the present invention is to provide a flame-retardant preoxidized fiber prepared by the method described in one of the objects of the present invention.

[0052] In the flame-retardant pre-oxidized fiber of the present invention, preferably, the limiting oxygen index of the flame-retardant pre-oxidized fiber is ≥50%, preferably 50% to 60%; for example, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60% and a range consisting of any two of the above values.

[0053] In the flame-retardant preoxidized fiber of the present invention, preferably,

[0054] The fiber density of flame retardant pre-oxidized fiber is 1.42~1.48g / cm 3 ; The fiber oxygen content of the flame retardant pre-oxidized fiber is 10 to 12 wt%; preferably 10.5 to 12 wt%.

[0055] In summary, the method for preparing flame-retardant preoxidized fiber of the present invention is to subject polyacrylonitrile precursor to unwinding, humidification, drying, gradient temperature preoxidation and winding to obtain flame-retardant preoxidized fiber. After active unwinding, the polyacrylonitrile precursor enters a continuous gradient temperature oxidation furnace, and the rotation speed of the three to seven rollers is controlled by online tension regulation to control the constant tension during the fiber feeding process. The tension of fibers with different k numbers is controlled between 800 and 2000 cN. The temperature of the oxidation furnace is controlled at 230 to 290 ° C, and the total oxidation time is 45 to 75 min. The bulk density of 1.42 to 1.48 g / cm can be prepared. 3 , flame retardant pre-oxidized fiber with an oxygen content of 10 to 12 wt% and a limiting oxygen index of 50 to 60%.

[0056] The third object of the present invention is to provide a flame-retardant pre-oxidized fiber prepared by the method described in one of the objects of the present invention or the use of the flame-retardant pre-oxidized fiber described in the second object of the present invention in the field of flame retardancy.

[0057] The endpoints and any values of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and a separate point value, and the separate point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0058] Compared with the prior art, the present invention has at least the following advantages:

[0059] The present invention provides a preparation method of flame-retardant pre-oxidized fiber and the flame-retardant pre-oxidized fiber, which can solve the problems of low limiting oxygen index and environmental unfriendliness of existing flame-retardant fibers and can effectively improve the performance of the flame-retardant fibers. DETAILED DESCRIPTION

[0060] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0061] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0062] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the scope of protection of the present invention.

[0063] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0064] The test instruments and test conditions used in the embodiments and comparative examples are as follows:

[0065] The oxygen content of pre-oxidized fiber was tested by elemental analyzer;

[0066] The density of pre-oxidized fiber body was tested using a density gradient tube;

[0067] The limiting oxygen index is tested using a limiting oxygen index tester.

[0068] [Example 1]

[0069] Flame-retardant preoxidized fibers were obtained by unwinding 6K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step employed active unwinding with a controlled tension of 600 cN. The humidification step involved immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involved feeding the fiber along a blowing direction in a tubular heating furnace, with the furnace temperature controlled at 115°C for 13 seconds. The preoxidation process employed gradient heating in an air atmosphere, using three blast-box oxidation furnaces connected in series. Five-roller mills were used for material transport, with the furnace temperatures set at 240°C (for oxidation furnace No. 1), 260°C (for oxidation furnace No. 2), and 280°C (for oxidation furnace No. 3). Constant tension was applied to the preoxidation process for the polyacrylonitrile-based fiber. The speed of the five-roller mill was controlled through online tension regulation, maintaining a constant tension of 900 cN throughout the fiber winding process. Each oxidation furnace had the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.246 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.338g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.433g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.3wt%; that of oxidation furnace No. 2 was 8.6wt%; and that of oxidation furnace No. 3 was 10.6wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 52.2%.

[0070] [Example 2]

[0071] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a tubular heating furnace with airflow at a controlled temperature of 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 240°C, 260°C, and 280°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.252 g / cm 3 The fiber density at the outlet of No.2 oxidation furnace is 1.345g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.446g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.5wt%; that of oxidation furnace No. 2 was 8.8wt%; and that of oxidation furnace No. 3 was 10.8wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 53.6%.

[0072] [Example 3]

[0073] Flame-retardant preoxidized fibers are produced by unwinding 96K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1600 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a tubular heating furnace with airflow at a controlled temperature of 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 240°C, 260°C, and 280°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1800 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.258 g / cm 3The fiber density at the outlet of No. 2 oxidation furnace is 1.352g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.453g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.7wt%; at the outlet of oxidation furnace No. 2, it was 9.1wt%; and at the outlet of oxidation furnace No. 3, it was 11.2wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 54.1%.

[0074] [Example 4]

[0075] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 245°C, 265°C, and 285°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.262 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.352g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.451g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 7.2wt%; at the outlet of oxidation furnace No. 2, it was 9.2wt%; and at the outlet of oxidation furnace No. 3, it was 11.3wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 54.8%.

[0076] [Example 5]

[0077] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three blast-box oxidation furnaces connected in series. A five-roller mill transports material before and after the oxidation furnaces, with the temperatures set at 245°C, 265°C, and 285°C, respectively. Constant tension is applied to the preoxidation process for the polyacrylonitrile-based fiber. The speed of the five-roller mill is controlled through online tension regulation, maintaining a constant tension of 1500 cN throughout the fiber feeding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 20 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.267 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.358g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.462g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 7.6wt%; that of oxidation furnace No. 2 was 9.8wt%; and that of oxidation furnace No. 3 was 11.8wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 55.6%.

[0078] [Example 6]

[0079] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1150 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a tubular heating furnace with airflow at a controlled temperature of 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three blast-box oxidation furnaces connected in series. A five-roller mill transports material before and after the oxidation furnaces, with the temperatures set at 245°C, 265°C, and 285°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1580 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 20 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.269 g / cm 3 The fiber density at the outlet of No.2 oxidation furnace is 1.362g / cm 3The fiber density at the outlet of No. 3 oxidation furnace is 1.468g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 7.8wt%; that of oxidation furnace No. 2 was 9.9wt%; and that of oxidation furnace No. 3 was 11.9wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 56.2%.

[0080] [Example 7]

[0081] Flame-retardant preoxidized fibers are obtained by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, preoxidizing with a gradient heating process, and then winding. The unwinding process uses active unwinding with a controlled tension of 600 cN. The humidification process involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying process involves feeding the fiber along a blowing direction in a tubular heating furnace, with the furnace temperature controlled at 115°C for 13 seconds. The preoxidation process uses a gradient heating process in an air atmosphere, employing three blower-box oxidation furnaces connected in series. A five-roller mill transports the material before and after the oxidation furnaces, with the temperatures set at 245°C, 265°C, and 285°C, respectively. Constant tension is applied to the preoxidation process for the polyacrylonitrile-based fiber. The speed of the five-roller mill is controlled through online tension regulation, maintaining a constant tension of 1580 cN throughout the fiber winding process. Each oxidation furnace has the same heat treatment time during the preoxidation process, with a residence time of 20 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.264 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.360g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.462g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 7.6wt%; at the outlet of oxidation furnace No. 2, it was 9.6wt%; and at the outlet of oxidation furnace No. 3, it was 11.5wt%. After pre-oxidation, the fibers were oiled and collected to produce flame-retardant pre-oxidized fibers. The fibers broke several times during the test, resulting in a limiting oxygen index of 54.3%.

[0082] The difference between Example 6 and Example 7 is the different tension control during the unwinding process. By comparing the results of Example 6 and Example 7, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 6 has a higher limiting oxygen index and a better flame retardant effect.

[0083] [Example 8]

[0084] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, using three blast-box oxidation furnaces connected in series. A five-roller mill transports material before and after the oxidation furnaces, with the temperatures set at 230°C, 265°C, and 280°C, respectively. Constant tension is applied to the preoxidation process for the polyacrylonitrile-based fiber. The speed of the five-roller mill is controlled through online tension regulation, maintaining a constant tension of 1500 cN throughout the fiber feeding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.236 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.341g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.415g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 4.8wt%; that of oxidation furnace No. 2 was 6.7wt%; and that of oxidation furnace No. 3 was 8.6wt%. After pre-oxidation, the fibers were oiled and collected to produce flame-retardant pre-oxidized fibers. Several fiber breakages occurred during the test, resulting in a limiting oxygen index of 40.3%.

[0085] The difference between Example 4 and Example 8 is that the temperature gradient during the pre-oxidation process is different. In Example 8, the temperature difference between the two oxidation furnaces is greater than 30 degrees. By comparing the results of Example 4 and Example 8, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 4 has a higher limiting oxygen index and better flame retardant effect.

[0086] [Example 9]

[0087] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 225°C, 260°C, and 295°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.223 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.3485g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.469g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 4.2wt%; that of oxidation furnace No. 2 was 6.3wt%; and that of oxidation furnace No. 3 was 10.9wt%. After pre-oxidation, the fibers were oiled and collected to produce flame-retardant pre-oxidized fibers. Several yarn breaks occurred during the test, and the limiting oxygen index of the flame-retardant pre-oxidized fibers was 40.1%.

[0088] The difference between Example 4 and Example 9 is that the temperature gradient in the pre-oxidation process is different. In Example 9, the temperature difference between the three oxidation furnaces is greater than 30 degrees. By comparing the results of Example 4 and Example 9, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 4, in which the temperature rise gradient in the pre-oxidation process is not higher than 30°C, has a higher limiting oxygen index and better flame retardant effect.

[0089] [Example 10]

[0090] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 240°C, 260°C, and 280°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 12 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.248 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.341g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.428g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.1wt%; at the outlet of oxidation furnace No. 2, it was 8.2wt%; and at the outlet of oxidation furnace No. 3, it was 9.2wt%. After pre-oxidation, the fibers were oiled and collected to produce flame-retardant pre-oxidized fibers. The fibers broke several times during the test, resulting in a limiting oxygen index of 39.8%.

[0091] The difference between Example 2 and Example 10 is that the residence time of each temperature zone during the pre-oxidation process is different. By comparing the results of Example 2 and Example 10, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 2 has a higher limiting oxygen index and a better flame retardant effect.

[0092] [Example 11]

[0093] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a blowing direction in a tubular heating furnace, controlled at 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 240°C, 260°C, and 280°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 2500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 12 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.251 g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.343g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.430g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.2wt%; that of oxidation furnace No. 2 was 8.3wt%; and that of oxidation furnace No. 3 was 9.4wt%. After pre-oxidation, the fibers were oiled and collected to produce flame-retardant pre-oxidized fibers. The fibers broke several times during the test, resulting in a limiting oxygen index of 38.5%.

[0094] The difference between Example 2 and Example 11 is that the stay in each temperature zone during the pre-oxidation process is different, and the tension during the wire feeding process during the pre-oxidation process is different. By comparing the results of Example 2 and Example 11, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 2 has a higher limiting oxygen index and better flame retardant effect.

[0095] [Example 12]

[0096] Flame-retardant preoxidized fibers are produced by unwinding 24K polyacrylonitrile precursor yarn, humidifying, drying, gradient-heating preoxidation, and winding. The unwinding step utilizes active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber along a tubular heating furnace with airflow at a controlled temperature of 115°C for 13 seconds. The preoxidation process utilizes gradient heating in an air atmosphere, employing three cascaded blower-type oxidation furnaces. A five-roller mill facilitates material transport, with the temperatures set at 240°C, 245°C, and 280°C, respectively. Constant tension is applied to the preoxidation process, with the five-roller mill's speed controlled by online tension regulation to maintain a constant tension of 1500 cN throughout the fiber's winding process. Each oxidation furnace maintains the same heat treatment time during the preoxidation process, with a residence time of 16 minutes per furnace. The fiber density gradually increases during the pre-oxidation process. The fiber density at the outlet of the No. 1 oxidation furnace is 1.252 g / cm 3 The fiber density at the outlet of No.2 oxidation furnace is 1.316g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.428g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.5wt%; that of oxidation furnace No. 2 was 6.9wt%; and that of oxidation furnace No. 3 was 8.8wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 30.1%.

[0097] By comparing the results of Example 12 and Example 2, it can be seen that in Example 12, the temperature rise gradient during pre-oxidation is only 5°C at one point. Compared with the condition in Example 2 in which the temperature rise gradient during the pre-oxidation process is controlled to be no higher than 30°C but no lower than 20°C, the flame-retardant pre-oxidized fiber prepared in Example 2 has a higher limiting oxygen index and a better flame retardant effect.

[0098] [Comparative Example 1]

[0099] Flame-retardant pre-oxidized fiber is obtained by unwinding 24K polyacrylonitrile precursor, humidifying, drying, gradient heating pre-oxidation, and winding. The unwinding step uses active unwinding with a controlled tension of 1050 cN. The humidification step involves immersing the unwinding precursor in pure water at room temperature for 7 seconds. The drying step involves feeding the fiber in a tubular heating furnace along the blowing direction, with the furnace temperature controlled at 115°C for 13 seconds. The pre-oxidation process uses gradient heating in an air atmosphere, employing three blast box oxidation furnaces connected in series. Five-roller conveyors are used for material transport, with the temperatures of the oxidation furnaces set at 240°C, 260°C, and 280°C, respectively. During the pre-oxidation process, polyacrylonitrile-based fibers are subjected to constant tension control. The speed of the five-roller mill is controlled by online tension regulation, and the tension of the fibers during the fiber feeding process is controlled. The tension of the No. 1 oxidation furnace is 2500cN, the tension of the No. 2 oxidation furnace is 1200cN, and the tension of the No. 3 oxidation furnace is 3000cN. During the pre-oxidation process, the heat treatment time of each oxidation furnace is the same, and the residence time of each oxidation furnace is 16 minutes. The fiber body density gradually increases during the pre-oxidation process, and the fiber body density at the outlet of the No. 1 oxidation furnace is 1.256g / cm 3 The fiber density at the outlet of No. 2 oxidation furnace is 1.346g / cm 3 The fiber density at the outlet of No. 3 oxidation furnace is 1.449g / cm 3 The oxygen content of the pre-oxidized fiber at the outlet of oxidation furnace No. 1 was 6.6wt%; that of oxidation furnace No. 2 was 8.8wt%; and that of oxidation furnace No. 3 was 10.9wt%. After pre-oxidation, the fibers were oiled and collected to obtain flame-retardant pre-oxidized fibers. No fiber breakage occurred during the test, and the resulting flame-retardant pre-oxidized fibers had a limiting oxygen index of 48.5%.

[0100] By comparing the results of Example 1 and Example 2, it can be seen that the flame-retardant pre-oxidized fiber prepared in Example 2 by controlling the tension of the fiber during the pre-oxidation process to be constant has a higher limiting oxygen index and better flame retardant effect.

[0101] Comparing the results of the above examples of the present invention with those of the comparative examples reveals that tension control during the unwinding of the precursor, tension control during the pre-oxidation process, pre-oxidation temperature, and dwell time in the oxidation furnace all affect the flame retardant effect and whether the fibers will break repeatedly during production. Clearly, the present invention utilizes specific process conditions to unwind, humidify, dry, pre-oxidize at a gradient temperature, and then wind up the polyacrylonitrile precursor to produce flame-retardant pre-oxidized fibers. This overcomes the issues of existing flame-retardant fibers with low limiting oxygen index and environmental friendliness, effectively improving the performance of flame-retardant fibers and enabling their use in the preparation of flame-retardant pre-oxidized fibers.

[0102] Compared with ordinary fibers, the flame-retardant fiber of the present invention has significantly lower flammability, significantly slows down the burning rate during combustion, can quickly self-extinguish after leaving the fire source, and releases less toxic smoke. It can be used in clothing, home furnishings, decoration and non-woven fabrics.

[0103] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0104] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0105] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0106] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A method for preparing flame-retardant preoxidized fiber, comprising the steps of unwinding raw silk and preoxidizing it; the preoxidation is carried out in a gradient temperature increase manner, and during the preoxidation, the tension of the fiber during the wire-feeding process is controlled to be constant.

2. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: The precursor comprises polyacrylonitrile precursor; and / or, The step of releasing the wire adopts an active wire releasing method; Preferably, when unwinding, the tension of the raw yarn is controlled to be 200 to 2000 cN; More preferably, The tension of the 3k-12k raw yarn is controlled to be 200-800cN; and / or, The tension of the 12k-48k raw yarn is controlled to be 800-1200cN; and / or, The tension of the raw yarn above 48K is controlled at 1200~2000cN.

3. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: The steps of humidification and drying are also included between the steps of laying out the raw silk and pre-oxidation; Preferably, the humidification step is to immerse the unwinding raw silk in water for 5-10 seconds at room temperature; and / or, The drying temperature is 110-120° C., and / or the drying time is 10-15 seconds.

4. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: The atmosphere during the pre-oxidation is an air atmosphere; and / or, The temperature gradient during the pre-oxidation process is not higher than 30°C, preferably the temperature gradient during the pre-oxidation process is not higher than 30°C, but not lower than 20°C; more preferably the temperature gradient during the pre-oxidation process is 20-25°C; Preferably, the pre-oxidation process is carried out in a three-temperature zone gradient heating manner, which are respectively recorded as the first temperature zone, the second temperature zone and the third temperature zone, wherein the temperatures of the first temperature zone, the second temperature zone and the third temperature zone increase in sequence.

5. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: During the pre-oxidation process, the tension of the fiber is controlled to be constant at any value between 800 and 2000 cN during the fiber feeding process; Preferably, Controlling the fiber tension of 3k to 12k to be constant at any value between 800 and 1200 cN; and / or, Controlling the fiber tension of 12k to 48k to be constant at any value between 1200 and 1600 cN; and / or, The fiber tension above 48K is controlled to be constant at any value between 1600 and 2000 cN.

6. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: In the pre-oxidation step, The pre-oxidation temperature is 230-290°C, and the total pre-oxidation time is 45-75 minutes; preferably, The starting temperature of the pre-oxidation is 230-250°C; preferably 235-245°C; and / or, The termination temperature of the pre-oxidation is 270-290°C; preferably 275-285°C; and / or, The pre-oxidation is carried out in a gradient temperature increase manner, wherein the pre-oxidation treatment time in each temperature zone is the same; preferably, the pre-oxidation treatment time in each temperature zone is 15 to 25 minutes.

7. The method for preparing the flame-retardant preoxidized fiber according to claim 4, wherein: The bulk density of the fiber during the pre-oxidation process is 1.23-1.48 g / cm 3 , and the bulk density of the fiber gradually increases during the pre-oxidation process; Preferably, the fiber density after pre-oxidation in the first temperature zone is 1.23-1.28 g / cm 3 and / or, The fiber density after pre-oxidation in the second temperature zone is 1.32-1.38 g / cm 3 and / or, The fiber density after pre-oxidation in the third temperature zone is 1.42-1.48 g / cm 3 .

8. The method for preparing the flame-retardant preoxidized fiber according to claim 4, wherein: The oxygen content of the fiber during the pre-oxidation process is 6 to 12 wt%, and the oxygen content of the fiber gradually increases during the pre-oxidation process; Preferably, The oxygen content of the fiber after pre-oxidation in the first temperature zone is 6 to 8 wt%; preferably 6.3 to 8 wt%; and / or, The oxygen content of the fiber after pre-oxidation in the second temperature zone is 8 to 10 wt %; preferably 8.5 to 10 wt %; and / or, The oxygen content of the fiber after pre-oxidation in the third temperature zone is 10-12 wt %, preferably 10.5-12 wt %.

9. The method for preparing the flame-retardant preoxidized fiber according to claim 1, wherein: After pre-oxidation, the steps of oiling and optionally collecting the yarn are also included.

10. A flame-retardant preoxidized fiber prepared by the method according to any one of claims 1 to 9.

11. The flame-retardant preoxidized fiber according to claim 10, characterized in that: The limiting oxygen index of the flame-retardant pre-oxidized fiber is ≥50%, preferably 50% to 60%.

12. Use of the flame-retardant pre-oxidized fiber prepared by the method according to any one of claims 1 to 9 or the flame-retardant pre-oxidized fiber according to any one of claims 10 to 11 in the field of flame retardancy.