JPS6347809B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing acrylonitrile-based flame-resistant fibers having high tensile elongation and knot elongation. More specifically, acrylonitrile fibers are treated in an oxidizing atmosphere under tension of 70 to 90% of the free shrinkage rate.
After flame-retardant treatment to equilibrium moisture content 6.5-15%, 150
The present invention relates to a method for producing flame-resistant fibers, which is characterized by shrinking the fibers by 0.5 to 20% in steam or hot water at temperatures below .degree. Conventionally, fibers obtained by heat-treating acrylonitrile fibers in an oxidizing atmosphere at 200 to 400°C are known as so-called acrylonitrile flame-resistant fibers. This flame-resistant fiber is used as a raw material for carbon fibers and fibrous activated carbon, and as it is, it is used as flame-resistant clothing, flame-resistant curtains, and insulation materials, and is also being applied to fields that utilize its chemical resistance. . However, this flame-resistant fiber has lower tensile strength and tensile elongation than the raw material acrylonitrile fiber, so it has poor processability, and it is difficult to shorten it during spinning or processing into nonwoven fabrics. It occurs frequently and the yield is poor. Furthermore, the resulting product also has poor abrasion resistance, and for this reason, the surface is usually treated with silicone resin or the like. As a result of research into these problems that conventional acrylonitrile-based flame-resistant fibers have, the present inventors found that flame-resistant fibers obtained by treating acrylonitrile-based fibers under specific conditions can solve these problems. . The present invention is as follows. Acrylonitrile fiber in an oxidizing atmosphere,
After flame-retardant treatment to equilibrium moisture content of 6.5-15% at 200-400℃ under tension of 70-90% of free shrinkage rate,
A method for producing an acrylonitrile flame-resistant fiber, which comprises shrinking it by 0.5 to 20% in steam or hot water at 150°C or lower. The flame-resistant fiber obtained by this method is
Fabrics made with high tensile strength and tensile elongation, and excellent workability such as spinnability,
Felt etc. have excellent wear resistance. The acrylonitrile fiber used as a raw material in the present invention is a fiber obtained from a polymer or copolymer containing 85% by weight or more of acrylonitrile, or a fiber obtained from a mixture of a polymer and a copolymer. In this case, the comonomer may be, for example,
(1) acrylic acid, methacrylic acid, (2) salts thereof,
Esters, acid chlorides, acid amides, N-substituted derivatives of acid amides, (3) vinyl chloride, vinylidene chloride, α-chloroacrylonitrile, vinylpyridines, (4) vinylsulfonic acid, allylsulfonic acid, vinylbenzene Examples include sulfonic acid, its alkali metals, and alkaline earth metal salts. The flameproofing treatment is performed as follows. Oxidation is carried out at 200 to 400°C for 0.3 to 20 hours in an oxidizing atmosphere, for example, in a single gas such as air, oxygen, hydrogen chloride, or sulfur dioxide gas, or in a medium of these and an inert gas. The tension applied during flameproofing treatment is adjusted so that it is 70 to 90% of the free shrinkage rate at that temperature.
The corresponding value is 0.01~0.3g/ if displayed separately.
It is d. If a strong tension is applied so that the free contraction rate is less than 70%, the fiber bundle becomes disordered and is likely to be cut, and if it exceeds 90%, the tension will break, which is inappropriate. Flame resistance is determined by the equilibrium moisture content of the fiber (25℃, RH80%)
Repeat until it reaches 6.5-15%. If the flame resistance is kept below 6.5%, hydrolysis occurs in the subsequent steam treatment step, resulting in a decrease in fiber strength and elongation, and poor spinnability. On the other hand, if the flame resistance is increased to more than 15%, the strength of the flame resistant fibers will decrease and fiber breakage will occur frequently during the crimp process. The fineness of the acrylonitrile fiber of the present invention is not particularly limited, but is preferably 0.5 to 14d, particularly 1.0 to 5d. If it is thinner than 0.5d, the fiber strength will be low and fiber breakage will easily occur.On the other hand, if it is thicker than 15d, the oxidation rate will be slow, and oxidation spots will occur inside and outside the fiber, causing yarn breakage and fuzz to occur frequently during spinning. . The fibers flameproofed in this way are then treated with steam or heated water. The processing temperature in this case is 150°C or less. If the temperature exceeds 150°C, the strength and elongation will decrease due to hydrolysis of the fiber surface. Particularly preferred is 80 to 130°C. The processing time is usually 1 minute to 2 hours, and becomes shorter as the processing temperature becomes higher. If the heating time is shorter than 1 minute, no effect of improving fiber performance will be observed. The effect can be promoted by impregnating phosphorus or boron compounds before steam treatment. Shrinks by 0.5 to 20% when treated with water vapor, etc. In this case, usually under no tension or 0.1g/d
Processed under tension of: Less than 0.5% or 20%
In both cases, strength and elongation decrease. The treatment with steam or hot water can be carried out in batches in an autoclave, or can be carried out continuously by sealing the outlet and inlet of the fiber bundle (tow) to be treated in a labyrinth manner. If steam treatment or hot water treatment is performed before the crimp treatment, the yield of the crimp treatment improves, but there is no particular problem if the steam treatment or hot water treatment is performed after the crimp treatment. Next, the present invention will be explained by examples. Example 1 93% by weight acrylonitrile, methyl acrylate
Single yarn fineness 3D obtained from a copolymer consisting of 5.0% by weight and 2.0% by weight of sodium metaallylsulfonate,
A fiber bundle (tow) consisting of 180,000 filaments is flame-resistant treated in an air atmosphere at 245°C under a tension such that the free shrinkage rate is 80%, and flame-resistant until each equilibrium moisture content shown in Table 1 below is achieved. The fibers were then treated with water vapor at a temperature of 125° C. until the shrinkage ratio became as shown in Table 1 below. The results shown in Table 1 were obtained.

[Table] (Note) , : Invention example, 1, 4: Comparative example The above table shows the performance of flame-resistant fibers after steam treatment of flame-resistant fibers with each equilibrium moisture content, compared to that before steam treatment. However, the results show that when the conditions specified in the present invention are adopted, a remarkable improvement in fiber performance is achieved. Example 2 The same acrylonitrile fiber bundle (tow) as in Example 1 was made flame resistant in air at 230°C for 3 hours and then at 270°C for 1.5 hours. Flame resistance was applied by applying tension so that the shrinkage rate during flame resistance was 75% of the free shrinkage rate at each flame resistance temperature. The resulting flame-resistant fiber had an equilibrium moisture content of 12%, a tensile strength of 18 Kg/mm ² , and a tensile elongation of 14.0%. This fiber is heated to a steam temperature of 125°C.
30 at a water vapor pressure (internal pressure) of 1.5 Kg/cm ² with a water yield rate of 5.5%.
2 minutes, and then apply a crimper nip pressure of 2Kg/cm ² .
Continuous treatment was carried out at a stuffing pressure of 1 Kg/cm ² and a feed rate of 95 m/hr to obtain crimped flame-resistant fibers. This fiber had a crimp number of 15.0, a crimp rate of 8.1%, a tensile strength of 22 Kg/mm ² and a tensile elongation of 29%. Example 3 Acrylonitrile 87% by weight, vinylidene chloride 10%
weight%, single yarn fineness 3d obtained from a copolymer consisting of 3.0% by weight methyl acrylate, number of constituent fibers
180000 filament fiber bundle (tow), Al ₂
(OH) _2.7 (SO ₄ ) _0.26 (PO ₄ ) _0.3 Cl It was treated with a basic aluminum chloride aqueous solution of _1.88 , impregnated with 0.04% Al, and the shrinkage rate was 1 hour at 250℃ and 1.3 hours at 270℃ in air at each temperature. Flame resistance was achieved under tension such that the free shrinkage rate was 75%. The resulting flame-resistant fiber had an equilibrium moisture content of 12.3%, a tensile strength of 23 Kg/mm ² and a tensile elongation of 21.5%. This fiber was further crimped with a nip pressure of 2Kg/cm ² ,
Continuous treatment was carried out at a stuffing pressure of 1 Kg/cm ² and a feed rate of 95 m/hr to obtain crimped flame-resistant fibers. The number of crimps was 14.1, and the crimp rate was 7.5%. Furthermore, when this fiber was treated under each treatment condition shown in Table 2 below, the results shown in Table 2 were obtained. According to these results, it is clear that excellent fiber performance and spinning processability can be obtained when the shrinkage rate is specified in the present invention.

【table】

[Table] Here, the fiber damage rate is calculated by weighing 20g of staple with a cut length of 51mm, applying it repeatedly to a sample card (Yamato Kiko Model SC-200) 10 times, and creating a staple diagram using the sorter method using the cotton length of the web. It was calculated using the following formula. Fiber damage rate (%) = (average fiber length of raw cotton) -
(Average fiber length after card test) / (Average fiber length of raw cotton) x 100 Short fiber content is the proportion of short fibers with a length of 1/2 or less of the average fiber length of raw cotton, as shown in the same staple diagram as above. be. Example 4 The same acrylonitrile fiber bundle (tow) as in Example 1 was mixed with basic aluminum chloride represented by Al ₂ (OH) _2.8 (SO ₄ ) _0.8 Cl _1.6 , ferric chloride, and hypophosphorous acid. Treated with mixed solution, Al200ppm,
Impregnated with Fe30ppm, P250ppm, 250℃ in air
It was then treated at 270° C. for 0.5 hours, under tension such that the shrinkage rate was 75% of the free shrinkage rate, and flame resistance was achieved. The resulting flame-resistant fiber had an equilibrium moisture content of 11.5%, a tensile strength of 29 Kg/mm ² and a tensile elongation of 34%. This was further treated for 30 minutes at a steam temperature of 125°C, a shrinkage rate of 7.1%, and a steam pressure (internal pressure) of 1.5 Kg/cm ² , and a crimper nip pressure of 2 Kg/cm ² and a stuffing pressure of 1 Kg/cm 2 .
cm ² and a feed rate of 95 m/hr to obtain crimped fibers. This fiber has a crimp number of 17.9,
The crimp rate was 9.4%, the tensile strength was 35 Kg/mm ² , and the tensile elongation was 39%.

Claims (1)

[Claims] 1 Acrylonitrile fibers are heated at 200 to 400°C under tension of 70 to 90% of free shrinkage in an oxidizing atmosphere.
After flame-retardant treatment to an equilibrium moisture content of 6.5 to 15% at
A method for producing acrylonitrile-based flame-resistant fiber, characterized by shrinking it.