JP2007051392A - Flame-resistant yarn - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-resistant yarn having high shape-retention to carbonization or exposure to flame and high processability. <P>SOLUTION: The flame-resistant yarn has a flame shrink-retention of ≥90% and a specific gravity of 1.40-1.44 and has ≥10 wrinkles having a groove depth of ≥0.15 μm and essentially continuously formed along the longitudinal direction of the yarn. The yarn can be produced by properly controlling the atmosphere temperature, retention time, etc., in the flame-resisting treatment of a precursor fiber to change the thermal history, residual elongation, etc., of the fiber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flame resistant yarn having high form retention and high workability.

  The flame resistant yarn is an oxidized fiber yarn obtained by heating in air at 200 ° C. to 300 ° C. using acrylonitrile fiber, cellulose fiber, phenol fiber, pitch fiber, etc. as a raw material. Because of its excellent properties, it is used as a heat insulating material, filler, reinforcing material, heat-resistant material, and sputter sheet. In addition, carbon fibers obtained by carbonizing the oxidized fibers are excellent in specific strength and specific elastic modulus. Therefore, various kinds of sports equipment, aerospace / base materials, CNG tanks, flywheels, windmills, roads / piers, etc. It is widely used as a material for structural substrates or their members / parts.

  Such a flame resistant yarn is often used as a woven fabric or a non-woven fabric. Therefore, it has sufficient processability, and in its actual use after processing, its form is not caused by exposure to flame or carbonization firing. Is required to hold. In order to improve the shape retention, it is effective to improve the shrinkage maintenance property at the time of flame exposure at the single yarn level, that is, the shrinkage resistance (shrinkage prevention property) before and after being exposed to the flame. In order to enhance this shrinkage maintenance property, the progress of flame resistance in the yarn cross-sectional direction is generally made deeper. However, if this is made too deep, the yarn becomes brittle and cannot withstand processing. However, if the progress of such flame resistance is made shallow, the shrinkage maintenance property is lowered, and the form retention property is lowered. Conventionally, this trade-off relationship has been a problem.

For example, as a means for improving workability, there is a method in which a metal ion is contained in a raw yarn and an oxidation treatment is performed (for example, refer to Patent Document 1). cause. In spun yarn, a method for controlling the weaving property by controlling the friction performance between the fiber and the fiber or metal has been proposed (for example, see Patent Document 2). As a result, there was a problem with the form maintainability during use at high temperatures after weaving and during carbonization.
Japanese Patent Publication No. 63-047808 JP 2004-124309 A

  An object of the present invention is to provide a flame-resistant yarn having high form-retaining property against carbonization or exposure to a flame and high workability.

  The present invention that achieves the above object is as follows. That is, the flame shrinkage maintenance ratio is 90% or more, the specific gravity is 1.40 to 1.44, and the ridge is formed substantially continuously in the longitudinal direction of the yarn, and the maximum depth of the concave portion is 0.15 μm. It is a flame resistant yarn having 10 or more wrinkles as described above.

  According to the present invention, as described below, it is possible to obtain a flame resistant yarn having high form retention and high workability.

  In the present invention, the term “flame resistance” is substantially synonymous with the term “flameproof” and includes the meaning of the term “hard twist”. Specifically, flame resistance is a general term indicating the property that combustion is difficult to continue, that is, the property of being difficult to burn.

  In the present invention, the flame resistant yarn refers to a fiber obtained by flameproofing an organic fiber such as polyacrylonitrile fiber, rayon fiber, or phenol fiber or pitch fiber as a precursor fiber. For example, a polyacrylonitrile fiber can be obtained by spinning an acrylonitrile polymer, coagulating and washing with drawing water, and appropriately applying an oil as necessary. The flameproofing treatment is usually performed by heat-treating the precursor fiber at 200 to 300 ° C. in an oxidizing atmosphere such as air.

  The flame resistant yarn of the present invention has a flame shrinkage maintenance rate of 90% or more. Here, the flame shrinkage maintenance rate means the resistance to shrinkage (shrinkage prevention) when exposed to the flame, and specifically refers to the shape retention before and after the exposure to the flame. As a measuring method, the flame-resistant fiber bundle is heated with a Bunsen burner, and the maintenance rate of the length is obtained to obtain the flame shrinkage maintenance rate.

Specifically, a flame resistant yarn bundle of about 400 mm is sampled and marked with a non-combustible material such as a clip so that the test length is 200 mm. Next, one end is fixed, a tension of 10 g per 3300 dtex is applied to the other end, and the marked test length is heated by a Bunsen burner flame. At this time, the Bunsen burner gas used is propane gas, the flame height is about 10 cm, and the distance between the marks is about 20 seconds / 200 mm in the length direction of the yarn by the upper 1/3 portion of the flame. Heat while moving halfway back and forth. Then, the length between marks is measured, this is set to Wb (mm), and flame shrinkage maintenance rate (%) is calculated | required according to the following formula | equation.
Flame shrinkage maintenance rate (%) = (Wb / 200) × 100
When the flame shrinkage maintenance rate is less than 90%, non-uniform shrinkage occurs during exposure to flame and carbonization and firing in actual use after processing, and the form cannot be kept stable.

  Moreover, it is important that the specific gravity of the flame resistant yarn of the present invention is 1.40 to 1.44. Such specific gravity can be obtained by the buoyancy method (Archimedes method) obtained from the difference in buoyancy between the density of the known liquid and the atmosphere. Here, the density of the known liquid is not particularly limited. For example, the mass of the flameproof yarn and the mass of water of the same volume are simultaneously measured, and the value ρ of the density of water at the temperature at the time of measurement is used. Can be sought. Actually, the method described in JIS R-7601 (1986) was followed. Specifically, 1.0 to 3.0 g of fiber is first collected and dried at 120 ° C. for 2 hours. Next, after measuring the absolute dry mass A (g), it was impregnated in a solvent bath having a known specific gravity (specific gravity ρ), and the fiber mass B (g) in the solvent bath was measured. Fiber specific gravity = (A × ρ) / The fiber specific gravity can be determined by (AB).

  If the specific gravity of the flameproof yarn is less than 1.40, even if the workability is good, the flameproof yarn itself may not have sufficient flameproofing ability, and the flameproof / sputtering performance of the processed product is insufficient. Or the strength of carbonized woven fabric / nonwoven fabric obtained by carbonization may decrease, or ignition may occur during carbonization. When the specific gravity of the flame resistant yarn exceeds 1.44, the brittleness of the flame resistant yarn becomes high. For this reason, single yarn breakage frequently occurs during processing, and the carbon fiber strength after carbonization of the processed product is low, which is not suitable for use.

  In addition, the flame resistant yarn of the present invention is a cocoon formed substantially continuously in the longitudinal direction of the yarn, and has 10 or more cocoons having a depth of the concave portion of 0.15 μm or more. Here, “substantially continuously formed” means that the wrinkles are not formed on the condition that the wrinkles formed extending in the longitudinal direction of the yarn are formed completely continuously over the entire yarn. Or, even if there is a portion with a depth of less than 0.15 μm, it means that it can be recognized as a single wrinkle as a whole. In addition, it does not necessarily require that the direction in which the wrinkles are generated is parallel to the longitudinal direction of the yarn, and it means that it is sufficient if it can be recognized as a wrinkle extending in the longitudinal direction of the yarn. However, for example, a portion where the depth of the concave portion is less than 0.15 μm exceeds 3% is not counted as one. In addition, those in which the direction is not uniform, for example, those in which the change in direction is severe and cannot be recognized as being entirely along the longitudinal direction of the yarn as a whole, are not counted as one. The presence / absence determination of wrinkles can be performed by counting substantially continuous wrinkles observed with a photograph of the fiber surface taken at a magnification of 7000 times using a scanning electron microscope (SEM). However, since it is not realistic to determine whether wrinkles are substantially continuous over the entire yarn, a method of taking a photograph of about 3 to 5 points at an arbitrary position and confirming the substantial continuity May be taken. As for the depth of the recess, the longest part of the depth can be measured by a photograph obtained by photographing the fiber cross section at a magnification of 7000 times in the same manner. By having such wrinkles, the resistance to shrinkage that occurs when exposed to flames, carbonization and firing, increases the rigidity due to the physical resistance caused by the form, compared with a smooth yarn of the same fineness As a result, form retention is improved. However, if the depth is less than 0.15 μm, the resistance effect does not appear, so it cannot be counted. If the number of wrinkles is 9 or less, the effect is insufficient.

  The flame resistant yarn of the present invention preferably has a tensile elongation of 20 to 30%. Here, the tensile elongation is measured based on JIS L-1015 (1999). If the tensile elongation is less than 20%, a weak yarn is generated during processing, which may cause a failure. On the other hand, if it exceeds 30%, it is too large, and it is not preferable because the thread breakage frequently occurs due to loose winding during the production of flame resistant yarn, resulting in poor productivity.

  Further, the flame resistant yarn of the present invention preferably has a phosphorus (hereinafter referred to as P) content in the fiber before the flame resistance treatment of 20 ppm by weight or less. Here, the P content is measured by the atomic absorption method after ashing a certain amount of sample at about 650 ° C. and then dissolving in diluted nitric acid. If the content is more than 20 ppm by weight, the development of quality such as strength and elongation required for processed products as impurities during flame resistance may be inhibited, which is not preferable.

  In the present invention, when the flame resistant yarn is processed, the number of filaments of the flame resistant yarn is preferably 20,000 to 100,000, preferably 30000 to 80,000. When the number of filaments is less than 30000, productivity at the time of processing decreases, whereas when it exceeds 80000, processing becomes difficult.

  In the present invention, the single yarn fineness of the precursor is preferably in the range of 1.1 to 3.3 dtex. Basically, the smaller the single yarn fineness, the less the flame breakage spots and the yarn breakage due to the heat accumulation in the fibers, and the better the processability of the flame resistant yarn. However, if the single yarn fineness is too small, the productivity will be low, so about 1.1 to 1.6 dtex is appropriate. On the other hand, if it is too large, breakage of yarn during production is likely to occur due to flame-resistant spots and heat accumulation in the fiber.

  The above-mentioned flame-resistant fibers are used for flame-proofing the precursor fibers obtained by appropriately controlling the DMSO concentration of the spun dimethyl sulfoxide (DMSO) aqueous solution, the draw ratio, etc., and the atmospheric temperature, residence time, etc. Can be obtained by appropriately controlling the temperature and changing the thermal history and residual elongation of the fiber. In general, the atmosphere during the flameproofing treatment is preferably in the air at a temperature of 200 ° C to 300 ° C. Furthermore, when obtaining a flame resistant yarn from polyacrylonitrile fiber as a raw material, a preferable temperature range is 220 ° C to 250 ° C. When the temperature is lower than 220 ° C., the residence time required for obtaining the necessary flame resistance is increased. On the other hand, when the temperature exceeds 250 ° C., if the residence time is long, the elongation of the flame resistant yarn and its workability may be lowered, which is not preferable. In particular, when flame resistance is achieved at 260 ° C. for about 100 minutes, the workability of the resulting flame resistant yarn may be deteriorated, which is not preferable. The residence time in such an atmosphere is influenced by the ambient temperature, but it is preferably in the range of 50 to 300 minutes, preferably 60 to 250 minutes. If the residence time is less than 50 minutes, the flameproofing temperature required for obtaining the flameproofing ability equivalent to that of the present invention becomes high, and yarn breakage due to heat accumulation in the fiber occurs, which is difficult to produce and is not preferable. When the temperature range is 200 to 250 ° C., the shape retention of the processed product is not sufficient when the residence time is about 50 minutes. Further, if the residence time exceeds 300 minutes, the brittleness of the flame resistant yarn proceeds due to the long-time treatment, and a single yarn breakage occurs during processing, which may be undesirable.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example, this invention is not limited at all by these Examples.

  In this example, the measurement of the flame shrinkage maintenance rate and the specific gravity was performed according to the method described above.

  Moreover, in this example, P measurement was measured by Hitachi 180-80 by the above-mentioned method. The elongation was measured by the method described above using TEXTTECHNO FAVIMAT. Moreover, about wrinkle measurement, the fiber surface was image | photographed with the magnification of 7000 times using the scanning electron microscope (SEM), and it measured from the photograph.

  Further, in this example, workability was judged from buckling and yarn cracking at the time of crimping, and twisting, cracking and operability at the time of check-off.

Further, the shape retention at the time of flame exposure and carbonization firing was performed by observing the wrinkled state after carbonization after the flame exposure per 1 m ² of the fabric before the flame exposure or before carbonization in the processed fabric. For example, when the sheet before carbonization is 100 cm long and 100 cm wide, there is no problem with the shape when the sheet after carbonization is 98 cm long and 99 cm wide. It is determined that a defect due to the occurrence has occurred.
Example 1
Acrylonitrile (AN) / Methyl acrylate (MEA) / Sodium methacryl sulfonate (SMAS) / Itaconic acid (IA) = 95.2 / 4.0 / 0.2 / 0.6 (molar ratio), intrinsic viscosity [η ] = 1.48 is dissolved in a DMSO solution, wet-spun in a DMSO solution at 30 ° C. and 60% by weight, stretched at a stretch ratio of 5 times, washed with water, oiled, etc. A precursor fiber bundle having a single fiber fineness of 1.4 dtex and a filament number of 48,000 was collected. This fiber bundle was subjected to a flameproofing treatment in an air atmosphere at a temperature of 220 ° C. for a residence time of 60 minutes and further at a temperature of 250 ° C. for a residence time of 100 minutes to obtain a flame resistant yarn. The flame-resistant yarn obtained has a flame shrinkage maintenance rate of 98%, a specific gravity of 1.42, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the recess of 0.15 μm or more. The number of was 10. The tensile elongation was 26%, and the P content in the fiber before the flameproofing treatment was 2 ppm by weight. This flame-resistant yarn had extremely good processability, and also had high form retention when the processed product was exposed to flame and carbonized.
(Example 2)
The precursor fiber collected in the same manner as in Example 1 except that the single fiber fineness is 2.7 dtex is flame resistant in an air atmosphere at a temperature of 200 ° C. for a residence time of 100 minutes, and further at a temperature of 230 ° C. for a residence time of 200 minutes. Treatment was applied to obtain a flame resistant yarn. The flame-resistant yarn obtained has a flame shrinkage maintenance rate of 97%, a specific gravity of 1.41, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the recess of 0.15 μm or more. The number of was 20. Further, the tensile elongation was 24% and the P content in the fiber before the flameproofing treatment was 1 ppm by weight. This flame-resistant yarn had good processability and high form retention when the processed product was exposed to flame and carbonized and fired.
(Comparative Example 1)
A flameproof yarn was obtained in the same manner as in Example 1 except that the residence time in the flameproofing treatment was changed to 60 minutes at a temperature of 220 ° C. and 50 minutes at a temperature of 250 ° C. The flame-resistant yarn obtained had a flame shrinkage maintenance rate of 84%, a specific gravity of 1.34, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the recess of 0.15 μm or more. The number of was 11. The tensile elongation was 28%, and the P content in the fiber before the flameproofing treatment was 10 ppm by weight. Although this flame-resistant yarn had good processability, it was not suitable for practical use because of its low form-retaining property when the processed product was exposed to flame and carbonized and fired.
(Comparative Example 2)
Flameproof yarn was obtained in the same manner as in Example 1 except that the temperature in the flameproofing treatment was changed to 200 ° C. for the first residence time of 60 minutes and 260 ° C. for the subsequent residence time of 100 minutes. The obtained flame resistant yarn has a flame shrinkage maintenance rate of 99%, a specific gravity of 1.48, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the concave portion of 0.15 μm or more. The number of was 11. The tensile elongation was 18%, and the P content in the fiber before flameproofing was 2 ppm by weight. This flame resistant yarn was not suitable for production because single yarn breakage occurred frequently during processing. Moreover, even if a processed product was made, the strength was low and it was not suitable for use.
(Comparative Example 3)
A flame resistant yarn was obtained in the same manner as in Example 1 except that the DMSO concentration of the spun DMSO aqueous solution in the precursor collection was changed to 80% by weight. The flame-resistant yarn obtained has a flame shrinkage maintenance ratio of 90%, a specific gravity of 1.42, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the recess of 0.15 μm or more. The number of was seven. The tensile elongation was 26%, and the P content in the fiber before the flameproofing treatment was 1 ppm by weight. Although this flame resistant yarn has no problem in workability, its shape retention at the time of exposure to flame and carbonization and firing of the processed product is low, and it was not suitable for practical use.
(Example 3)
A flame resistant yarn was obtained in the same manner as in Example 1 except that the draw ratio in collecting the precursor was changed to 6 times. The single fiber fineness of the collected precursor fiber is 1.2 dtex, the flame shrinkage retention rate of the obtained flame resistant yarn is 98%, the specific gravity is 1.42, and it is formed substantially continuously in the longitudinal direction of the yarn. The number of wrinkles in which the depth of the recesses was 0.15 μm or more was 10. The tensile elongation was 17%, and the P content in the fiber before the flameproofing treatment was 2 ppm by weight. Although this flame resistant yarn sometimes caused trouble in processing due to weak yarn at the time of processing, the shape retention at the time of carbonization firing was high when the processed product was exposed to flame.
Example 4
A flame resistant yarn was obtained in the same manner as in Example 1 except that the draw ratio in collecting the precursor was changed to 3 times. The single fiber fineness of the collected precursor fiber is 1.6 dtex, the flame shrinkage retention rate of the obtained flame resistant yarn is 96%, the specific gravity is 1.42, and it is formed substantially continuously in the longitudinal direction of the yarn. The number of wrinkles in which the depth of the recesses was 0.15 μm or more was 10. The tensile elongation was 34%, and the P content in the fiber before the flameproofing treatment was 2 ppm by weight. This flameproof yarn was frequently wound during the flameproofing process, and stable production was difficult, but the obtained flameproof yarn had good workability and retained its shape when the processed product was exposed to flame and carbonized and fired. The nature was also high.
(Example 5)
A flame resistant yarn was obtained in the same manner as in Example 1. In the precursor fiber production process, water containing 40 wt ppm of orthophosphoric acid as P was used during washing with water. The flame-resistant yarn obtained has a flame shrinkage maintenance rate of 98%, a specific gravity of 1.42, a cocoon formed substantially continuously in the longitudinal direction of the yarn, and a depth of the recess of 0.15 μm or more. The number of was 10. The tensile elongation was 26%, and the P content in the fiber before the flameproofing treatment was 60 ppm by weight. This flame-resistant yarn had very good workability and had high form-retaining properties when the processed product was exposed to flame and carbonized and fired, but the strength after carbonization was low.

Claims (3)

  The flame shrinkage maintenance rate is 90% or more, the specific gravity is 1.40 to 1.44, and the ridge is formed substantially continuously in the longitudinal direction of the yarn, and the maximum depth of the concave portion is 0.15 μm or more. A flame resistant yarn having 10 or more wrinkles.   The flame resistant yarn according to claim 1, having a tensile elongation of 20 to 30%.   The flameproof yarn according to any one of claims 1 to 2, which is obtained by flameproofing a fiber having a phosphorus content of 20 ppm by weight or less before the flameproofing treatment.