JP2008156800A - Flame-resistant meta-type wholly aromatic polyamide fibers - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide meta-type wholly aromatic polyamide fibers improved in a hardening phenomenon caused by carbonization under exposure to flames. <P>SOLUTION: The meta-type wholly aromatic polyamide fiber is a fiber which includes an acid anhydride-based cross-linking agent in an amount of 0.01-10 pts.wt. based on the weight of the wholly aromatic polyamide, and has improved hardening phenomenon caused by carbonization under exposure to flame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a meta-type wholly aromatic polyamide fiber having improved heat shrinkage characteristics. More specifically, the present invention relates to a novel flame-resistant meta-type wholly aromatic polyamide fiber containing an acid anhydride-based crosslinking agent that can suppress a curing phenomenon due to carbonization when contacting a high-temperature flame or fireball.

  Conventionally, it is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy, and these wholly aromatic polyamides are amide polar It is also well known that it is soluble in a solvent and can be formed into a fiber from a polymer solution in which a wholly aromatic polyamide is dissolved in the solvent by a method such as dry spinning, wet spinning, semi-dry semi-wet spinning, or the like. Among such wholly aromatic polyamides, fibers of meta-type wholly aromatic polyamides typified by polymetaphenylene isophthalamide (sometimes generally referred to as “meta-aramid”) are particularly useful as heat-resistant and flame-retardant fibers. It is used in fields that exhibit these characteristics, for example, industrial applications such as heat-resistant filters and electronic parts, and disaster prevention and safety applications such as protective clothing that emphasizes heat resistance, flame resistance, flame resistance, etc. Yes. Among these, protective clothing includes pre-furnace protective clothing worn in front of high-temperature furnaces such as blast furnaces, electric furnaces, and incinerators, fire-proof clothing for people engaged in fire fighting work, and welding protective clothing for welding work exposed to high-temperature sparks. It is widely used as a flame-retardant work wear for people who handle highly flammable chemicals.

  Meta-type wholly aromatic polyamide fibers have excellent heat resistance, flame retardancy, and self-digestibility, and general yarn quality is natural fibers such as clothing fibers, cotton and wool, and synthetic materials such as nylon, polyester, and acrylic. Because it is very similar to fiber, it is more protective than glass fiber, asbestos fiber, phenolic resin fiber, metal foil coating material, etc. used in conventional protective clothing in terms of processability, comfort, washability, and clothes. It is recognized as an excellent clothing material.

  However, conventional protective clothing made of meta-type wholly aromatic polyamide fibers may cause material shrinkage and perforation when it comes into contact with high-temperature flames or fireballs. Therefore, there are limits to the range of fire fighting and lifesaving activities. Therefore, if the fire resistance, flame resistance, heat resistance, etc. of the protective clothing material made of meta-type wholly aromatic polyamide fiber is dramatically improved, for example, fire extinguishing activities will enter the fire site regardless of the progress of the fire. This enables early fire extinguishing / rescue activity, and even in the heyday of fire, it is possible to extinguish fire quickly by injecting water close to the source of fire. As a result, there are expected merits such as drastically reducing water loss in fire fighting activities, realizing quick and early rescue, and improving safety of fire fighters.

  For this reason, in order to improve the fireproof performance as a protective clothing material made of meta-type wholly aromatic polyamide fiber, it is desired to suppress a hardening phenomenon caused by carbonization of the material particularly when it comes into contact with a high-temperature flame or a fireball.

  Conventionally, in order to improve the flame resistance of wholly aromatic polyamide fibers, a method of adding an organophosphorus compound, a phosphorus-containing phenol resin, a halogen compound, etc. to a polymer has been proposed, and a method of blending a halogen atom-containing organophosphorus compound Has been proposed (see Patent Document 1 below). However, although this method can improve the dimensional stability, it does not improve the hardening phenomenon due to carbonization that occurs during exposure to flame, and has a problem in expanding the use as protective clothing.

  Further, a fiber excellent in dimensional stability at high temperature and a method for producing the same made of a blend of a wholly aromatic polyamide and a soluble resin such as polycarbonate, polyethersulfone, polysulfone, polyarylate, and polysulfidesulfone have been proposed (see below). Patent Document 2). However, in this method, there is no mention of the shrinkage of the material when it comes into contact with a high-temperature flame or fireball, that is, the curing phenomenon at high temperature. It can be easily imagined that the curability is not excellent due to carbonization.

  As another method, for the purpose of improving the fire resistance when exposed to flame, crosslinking is performed by high-temperature heat treatment of aromatic polyamide fibers in an inert atmosphere containing IV, V and VI halides and oxyhalides. A method for forming a structure (see Patent Document 3 below), a method for forming a crosslinked structure by high-temperature heat treatment in an inert atmosphere containing a halogen-substituted phosphazene (see Patent Document 4 below), and a high-temperature air atmosphere A method of forming an oxidative crosslink by treating fibers for a long time (see Patent Documents 5 and 6 below) and the like has been proposed. There is a problem that productivity is not good.

  In addition, a method of immersing and impregnating an aromatic polyamide fiber in an inorganic phosphoric acid solution to form a crosslinked structure (see Patent Document 7 below) has also been proposed. Although mention is made of stability improvement, there is a description that carbonization occurs when exposed to flame, and the hardening phenomenon due to carbonization is not improved.

  Furthermore, in recent years, a method of forming an aromatic polyamide fiber having a crosslinked structure with sulfur (see Patent Document 8 below), a method of impregnating polybenzimidazole and aromatic polyamide fiber with hexavalent tungsten to form a crosslinked structure (Patent Document below) (Ref. 9) has been proposed, but the former refers to the improvement of mechanical strength, the latter refers to the improvement of fire resistance, but only advocates an improvement in weight reduction. Not mentioned.

JP-A-53-122817 JP-A-5-321026 Japanese Patent Publication No. 47-5436 Japanese Patent Laid-Open No. 49-132398 Japanese Patent Publication No.46-419 JP 49-35614 A JP 50-114473 A JP 2000-512694 A Japanese National Patent Publication No. 8-503504

  The present invention has been made to solve the problems of the prior art as described above, and its main purpose is to provide a novel flame-resistant meta-type wholly aromatic polyamide fiber that has improved the hardening phenomenon caused by carbonization under exposure to flame. It is to provide.

  According to the present invention, as a meta-type wholly aromatic polyamide fiber that solves the above problems, a meta containing 0.01 to 10% by weight of an acid anhydride-based crosslinking agent based on the weight of the meta-type wholly aromatic polyamide. A fully aromatic polyamide fiber of the type that provides a significantly improved cure phenomenon due to carbonization under flame exposure.

  That is, the present invention contains 0.01 to 10 parts by weight of a cross-linking agent composed of an aromatic polycarboxylic acid anhydride per 100 parts by weight of the wholly aromatic polyamide constituting the meta-type wholly aromatic polyamide fiber. The present invention relates to a flame-resistant meta-type wholly aromatic polyamide fiber.

A preferred embodiment of the flame-resistant meta-type wholly aromatic polyamide fiber of the present invention is characterized in that the acid anhydride crosslinking agent is an aromatic polycarboxylic acid anhydride is pyromellitic acid anhydride.
The preferred flame resistant meta type wholly aromatic polyamide fiber of the present invention is characterized in that its tensile strength is 2.9 cN / dtex or more.

  The flame-resistant wholly aromatic polyamide fiber of the present invention contains a specific amount of a cross-linking agent composed of an aromatic polycarboxylic acid anhydride, so that the heat shrinkability at a high temperature becomes extremely small, and contacts a high-temperature flame or fireball. However, it is possible to provide various fiber products that are less likely to cause problems such as perforation and have excellent flame resistance. For this reason, it is extremely useful particularly in the development of materials for use in protective clothing.

  The meta-type wholly aromatic polyamide in the present invention is a polyamide produced by, for example, solution polymerization or interfacial polymerization using a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid halide as raw materials. For example, other copolymer components such as the para type may be copolymerized within a range that does not inhibit the above.

  Examples of the meta-type aromatic diamine include metaphenylene diamine, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone and the like, and substitution of halogens and alkyl groups having 1 to 3 carbon atoms on these aromatic rings. Derivatives having a group such as 2,4-toluylenediamine, 2,6-toluylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene and the like can be used. Among these meta-type aromatic diamines, metaphenylene diamine or the above mixed diamine containing 70 mol% or more of metaphenylene diamine is preferable.

  Examples of the meta-type aromatic dicarboxylic acid halide include isophthalic acid halides such as isophthalic acid chloride and isophthalic acid bromide, and derivatives having substituents such as halogen and an alkoxy group having 1 to 3 carbon atoms on the aromatic ring, such as 3-Chloroisophthalic acid chloride, 3-methoxyisophthalic acid chloride can be used. Especially, said mixed carboxylic acid halide containing 70 mol% or more of isophthalic acid chloride or isophthalic acid chloride is preferable.

In addition to the above diamines and dicarboxylic acid halides, copolymer components that can be used as needed include, as aromatic diamines, paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, amino Benzene derivatives such as anisidine, 1,5-naphthylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ketone, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylmethane, etc. On the other hand, as aromatic dicarboxylic acid halides, terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4'-biphenyldicarboxylic acid chloride, 4,4'-diphenyl ether dicarboxylic acid And acid chloride That. The copolymerization ratio of these copolymerization components is preferably 20 mol% or less based on the total acid component of the polyamide, since the properties of the meta-type wholly aromatic polyamide are liable to deteriorate if it is too large. In particular, a suitable meta-type wholly aromatic polyamide is a polyamide in which 80 mol% or more of all repeating units are composed of metaphenylene isophthalamide units, and among them, polymetaphenylene isophthalamide is preferable.
The degree of polymerization of the meta-type wholly aromatic polyamide is suitably in the range of 1.3 to 3.0 as the intrinsic viscosity (IV) measured using concentrated sulfuric acid at 30 ° C. as a solvent.

  In the flame-resistant meta-type wholly aromatic polyamide fiber of the present invention, 0.01 to 10 parts by weight of a crosslinking agent comprising an aromatic polycarboxylic acid anhydride based on 100 parts by weight of wholly aromatic polyamide constituting the fiber. , Preferably 0.05 to 5 parts by weight. If the content of the cross-linking agent is less than the above range, there is almost no effect of suppressing the curing phenomenon caused by carbonization when contacting the high-temperature flame or fireball, which is the object of the present invention. In addition to the decrease in mechanical properties, the effect of suppressing the curing phenomenon due to carbonization also decreases.

  The cross-linking agent used in the present invention is not particularly limited as long as it is an aromatic polycarboxylic acid anhydride having a function of cross-linking at least a part of the polymer in the yarn production stage including heat treatment. Pyromellitic anhydride (1,2,4,5-benzenetetracarboxylic dianhydride) is particularly preferred.

  Such a flame resistant meta-type wholly aromatic polyamide fiber of the present invention has a tensile strength of 2.9 cN / dtex or more, particularly 3.0 to 5.0 cN / dtex, and protective clothing that makes use of the flame resistance, etc. It is preferable for use in various applications.

  Such a meta-type wholly aromatic polyamide fiber of the present invention has an excellent effect of suppressing the carbonization and hardening phenomenon when exposed to flame, and the suppression mechanism is that the meta-type all-aromatic polyamide fiber is generated by heat during fiber spinning / processing or exposure to flame. This is considered to be because the carbonization phenomenon that is likely to occur in conventional wholly aromatic polyamides can be suppressed by the crosslinked structure between the polymer molecules of the aromatic polyamide.

In order to produce the meta-type wholly aromatic polyamide fiber of the present invention as described above, for example, meta-type wholly fragrance in which a predetermined amount of a crosslinking agent made of an aromatic polycarboxylic acid anhydride such as pyromellitic acid anhydride is added. It can be produced by preparing a solution of a group polyamide, spinning the solution as a dope for spinning, then washing with water if necessary, and drawing and heat treatment. At this time, it is preferable that the maximum temperature in the heat treatment is 250 to 400 ° C., because effective crosslinking occurs inside the meta-type wholly aromatic polyamide constituting the fiber.
The heat treatment may be a heat treatment under tension, but is preferably performed while relaxing about 10 to 30%.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by these. In addition, each physical-property value in an Example and a comparative example was measured with the following method.

<Intrinsic viscosity (IV)>
The polymer was dissolved in 97% concentrated sulfuric acid and measured at 30 ° C. using an Ostwald viscometer.
<Fineness>
It measured according to JIS-L-1015.
<Strength and elongation>
According to JIS-L-1015, the sample length was 20 mm, the initial load was 0.44 mN / dtex, and the extension rate was 20 mm / min.
<Evaluation of degree of cure when exposed to flame>
A needle felt having a basis weight of 100 g / m ² was prepared from the fiber sample, and the end surface of the sample was gripped by a metal frame of 5 cm long × 5 cm wide. The sample prepared as described above was exposed to a flame for 5 seconds with a gas burner having a flame temperature of 500 ° C. The sample after the flame exposure was cut into 4cm length x 1cm width, and the degree of cure was evaluated by the sample hanging length (mm) when a weight of 2.0g was applied to the sample vertical end surface with the vertical center as a fulcrum. did. Here, those with a hanging length exceeding 14 mm were ranked as good in flexibility (◯), those with 10 to 14 mm were slightly defective (Δ), and those with less than 10 mm were ranked as defective.

[Example 1]
0.19 parts by weight of pyromellitic anhydride was added to 7.6 parts by weight of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) and stirred to obtain Solution A. Further, 19.4 parts by weight of polymetaphenylene isophthalamide having IV = 1.9 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863 is dissolved in 72.8 parts by weight of NMP to obtain a transparent polymer. Solution B was obtained.
The solution A and the polymer solution B thus obtained were mixed and stirred to form a polymer solution comprising 19.4 parts by weight of polymetaphenylene isophthalamide, 0.19 parts by weight of pyromellitic acid anhydride and 80.4 parts by weight of NMP. C was obtained.

  This polymer solution C was heated to 85 ° C. to prepare a dope for spinning (spinning raw solution), and spun by discharging it from a spinneret having a hole diameter of 0.07 mm and a hole number of 100 into a coagulation bath at 85 ° C. The composition of the coagulation bath was 40% by weight of calcium chloride, 5% by weight of NMP, and the remaining 55% by weight was water. The spun yarn was passed through this coagulation bath at an immersion length (effective coagulation bath length) of 100 cm at a yarn speed of 7.0 m / min, and then pulled out into the air.

  The coagulated yarn was washed with water through the first and second aqueous washing baths, and the total immersion time in the washing bath was 50 seconds. An NMP aqueous solution (concentration 20% by weight) having a temperature of 30 ° C. was used as the first aqueous cleaning bath, and an NMP aqueous solution (concentration 10% by weight) having a temperature of 30 ° C. was used as the second aqueous cleaning bath. Next, this washed yarn was stretched 4.0 times in 75 ° C. water and immersed in warm water of 60 ° C. for 48 seconds. Next, the film was wound around a roller having a surface temperature of 130 ° C. and dried, and then subjected to a relaxation heat treatment of 0.80 times on a hot plate having a surface temperature of 360 ° C. to obtain polymetaphenylene isophthalamide fibers.

The physical properties of the obtained fiber were a fineness of 2.20 dtex, a strength of 3.12 cN / dtex, and an elongation of 61%.
Table 1 shows the physical properties of the fibers and the results of evaluation of the degree of curing when exposed to flame using the fibers as needle felt.

[Examples 2 to 4]
In Example 1, spinning, stretching, and relaxation heat treatment were performed under the same conditions as in Example 1 except that the pyromellitic anhydride content was changed as shown in Table 1. The evaluation results of the obtained fiber are shown in Table 1.

[Comparative Example 1]
In Example 1, spinning, stretching, and relaxation heat treatment were performed in the same manner as in Example 1 except that a spinning stock solution containing no pyromellitic anhydride was used. The evaluation results of the obtained fiber are shown in Table 1.

[Comparative Example 2]
In Example 1, spinning, stretching, and relaxation heat treatment were performed under the same conditions as in Example 1 except that the pyromellitic anhydride content was changed as shown in Table 1. The evaluation results of the obtained fiber are shown in Table 1.

  The flame-resistant meta-type aromatic polyamide fiber according to the present invention has a very good heat shrinkage property at high temperatures, and provides a fiber product that is less prone to problems such as perforation even when it comes into contact with a high-temperature flame or fireball. It is particularly useful as a material for protective clothing applications.

Claims (3)

  The meta-type wholly aromatic polyamide fiber is characterized by containing 0.01 to 10 parts by weight of a crosslinking agent made of an aromatic polycarboxylic acid anhydride per 100 parts by weight of wholly aromatic polyamide constituting the fiber. Flame resistant meta-type wholly aromatic polyamide fiber.   The flame-resistant meta-type wholly aromatic polyamide fiber according to claim 1, wherein the aromatic polycarboxylic acid anhydride is pyromellitic acid anhydride.   3. The flame resistant meta-type wholly aromatic polyamide fiber according to claim 1, wherein the fiber has a tensile strength of 2.9 cN / dtex or more.