JP3301509B2 - Heat and flame resistant fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant and flame-resistant cloth, and more particularly, to a heat-resistant and flame-resistant garment represented by fire-fighting clothes and heat-resistant work clothes, a fire-blocking layer or a heat- and flame-resistant sheet. It concerns a suitable fabric.

[0002]

2. Description of the Related Art Hitherto, heat-resistant and flame-resistant clothes using heat-resistant and flame-retardant materials, fire blocking layers, and the like have been developed, and the fabric constituting the heat-resistant and flame-resistant clothes contains a flame retardant. Cotton (known as FR cotton, etc.), aromatic meta-aramid (trade name: Conex, Nomex, etc.), aromatic para-aramid (trade name: Kevlar, etc.), polybenzimidazole or blends thereof are known. Has been put to practical use. However, the heat-resistant temperature of these fibers is at most 400 ° C. to 500 ° C. when evaluated based on the decomposition temperature, and further high-performance fibers are required. On the other hand, polybenzazole fibers having extremely high heat resistance and flame retardancy have been developed, and their practical use as heat-resistant and flame-resistant fabrics is expected.

It has been suggested that as a factor controlling the heat and flame resistance characteristics of the above heat and flame resistant fabric, the moisture content of the material naturally influences the heat resistance and flame retardancy of the material itself. (See, for example, Lee et al., J. Fir.
e Sci., 4, 315 (1986) and Barker et al., Text.
Res. J., 57 (6), 331 (1987)). The above-mentioned polybenzazole fiber has an equilibrium moisture content of about 2%, and when applied to heat-resistant and flame-resistant fabrics, the equilibrium moisture content of the polybenzazole fiber is very small, so
There was a problem that the flame resistance was not sufficiently exhibited.

[0004]

SUMMARY OF THE INVENTION The present invention is to further improve the low equilibrium moisture content which has been a cause of insufficient heat and flame resistance when polybenzazole fiber is applied as a heat and flame resistant fabric. Excellent heat resistance,
It is intended to provide a flame resistant fabric material.

[0005]

Means for Solving the Problems As a result of diligent studies of the method for solving the above-mentioned problems, the present inventors have found that a polybenzazole fiber produced by a preferred production method has a high equilibrium moisture content. The inventors have found that a fabric having excellent heat and flame resistance can be obtained, and have reached the present invention. That is, the present invention provides a heat- and flame-resistant cloth, which is a cloth using at least a part of a fiber made of a polybenzazole polymer, wherein the fiber has a substantial equilibrium moisture content of 5% or more. Still more preferably, the weight fraction of the polybenzazole fiber is 50% or more, more preferably 80% or more.
% Of heat-resistant and flame-resistant fabrics.

In the present invention, the polybenzazole fiber is a fiber made of a polybenzazole polymer, and the polybenzazole (PBZ) is a polybenzoxazole (PBO) homopolymer, a polybenzothiazole (PBZ).
BT) Homopolymer and a random, sequential or block copolymer of PBO and PBT. Here, polybenzoxazole, polybenzothiazole and their random, sequential or block copolymers are described, for example, in Wolfe et al.
d Crystalline Polymer Compositions, Process and Pr
oducts "US Patent 4,703,103 (October 27, 1987),
`` Liquid Crystalline Polymer Compositions, Process
and Products "USPatent 4,533,692 (August 6, 19
85), "Liquid Crystalline Poly (2,6-Benzothiazole)
Compositions, Process and Products '' USPatent
4,533,724 (August 6, 1985), "Liquid Crystalline
Polymer Compositions, Process and Products '' USP
atent 4,533,693 (August 6,1985), Evers's "Thermo
oxidatively Stable Articulated p-Benzobisoxazolean
d p-Benzobisthiazole Polymers '' USPatent 4,359,56
7 (November 16, 1982), Tsai et al.
Heterocyclic Block Copolymer '' US Patent 4,578,432
(March 25, 1986).

The structural units contained in the PBZ polymer are preferably selected from lyotropic liquid crystal polymers. The monomer units are described in structural formulas (a)-(h). The polymer preferably consists essentially of monomer units selected from structural formulas (a)-(h):
More preferably, it consists essentially of monomer units selected from structural formulas (a)-(c).

[0008]

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[0009]

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[0010] Suitable solvents for forming the dope of the PBZ polymer include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

The solution concentration of the polymer is preferably at least about 7% by weight, more preferably at least 1%.
0% by weight, most preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as, for example, polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration is usually 20% by weight
Never exceed.

[0012] Suitable polymers, copolymers or dopes are synthesized by known techniques. For example, Wolfe et al.
U.S. Patent 4,533,693 (August 6,1985); Sybert et al.
S. Patent 4,772,678 (September 20,1988), Harris U.
See S. Patent 4,847,350 (July 11,1989). PBZ
Polymers are described in US Patent 5,089,591 by Gregory et al.
ary 18, 1992), it is possible to increase the molecular weight at a high reaction rate under relatively high temperature and high shear conditions in a dehydrating acid solvent.

The dope in which the polybenzazole polymer is dissolved in a solvent is produced by a known dry-wet spinning method.
That is, the dope is discharged from the spinneret, and the fibrous dope passes through the gas, and then comes into contact with the liquid to form a yarn. The method of separating the PBZ polymer from the fibrous dope is known as coagulation. Spinning and coagulation technology
U.S. Patent 4,263,245 (April 21, 1981); Wolfe et al.
S. Patent 4,533,693 (August 6, 1985), Adams et al.
Marerials Science and Engineering of Rigid Rod Po
lymers '' pp247-49, pp259-60 (Marerials Reaearch Soc
society 1989).

The fibrous dope that has passed through the gas is brought into contact with a fluid. The liquid may be in the form of a vapor, but is preferably a liquid. The liquid is brought into contact with the fibers in a liquid bath or by spraying. The liquid is water or a mixture of water and an acid, preferably a phosphoric acid solution having a concentration of 30% by weight or less.

After coagulation, the residual solvent in the fibers is further washed with a fluid. The coagulation fluid and the cleaning fluid may be the same or different. The washing is performed continuously until the residual solvent in the fiber reaches a predetermined concentration. When the solvent is polyphosphoric acid, the residual solvent concentration in the fiber is preferably about 5000 ppm or less, more preferably about 3 ppm.
000 ppm or less. The washed fibers usually have a washing liquid or residual coagulating liquid of 30% by weight or more. If necessary, the washed yarn may be neutralized.

The washing liquid or residual coagulating liquid is dried in a heating zone provided continuously or discontinuously. The heating zone is, for example, an electric furnace, a heating roller or a heating inert gas, or a combination thereof. Regardless. When an electric furnace, a heating roller, or the like is used as the heating zone, the atmosphere may be air, but an inert gas atmosphere such as nitrogen, helium, or argon is preferable.

The fabric in the present invention refers to a structure formed from long fibers (filaments) or short fibers (staples), regardless of the structure. For example,
Examples include fabrics and knits having a plain weave, satin weave, twill weave, or other structure composed of filaments, spun yarns, or composite yarns thereof, and nonwoven fabrics obtained from staples by a technique such as needle punching or water punching, and laminates thereof. . Further, a combination thereof may be used. The cloth containing polybenzazole refers to a cloth containing preferably 20% or more by weight of polybenzazole,
More preferably, the fraction contains 50% or more, most preferably 80% or more. This fraction can be optimized according to the required heat and flame resistance characteristics. The fibers mixed here are preferably heat-resistant fibers such as meta-aramid, para-aramid, polybenzimidazole, polyimide, and acrylic flame-resistant fibers, and fibers such as flame-retarded cotton, wool, and rayon.

The term "substantially equilibrium moisture content" means the weight fraction of moisture when left in an atmosphere at a temperature of 20 ° C. and a humidity of 65% until no change in moisture content is substantially observed. The equilibrium is reached after standing for 30 to 40 days under the conditions described above. A feature of the present invention is that a fabric having an equilibrium moisture content of 5% or more has been achieved for the first time.

As a result of intensive studies to obtain fibers having a substantially equilibrium moisture content of 5% or more, it was found that the above-mentioned drying step can be achieved by performing the following recommended conditions. That is, the drying conditions are adjusted so that the moisture content after the drying step is 5% or more, and preferably, the drying time is adjusted such that the moisture content after the drying process is 5% or more at a drying temperature of 140 ° C. or more. And more preferably 180
The drying time is adjusted so that the moisture content after the drying step is 5% or more at a drying temperature of not less than ° C. Here, the drying temperature is the highest drying temperature. For example, in the case where drying is performed in multiple stages, it refers to the process with the highest temperature. The drying time can be adjusted by changing the effective zone length for drying. Although the mechanism by which the equilibrium moisture content of the fiber obtained under these recommended conditions becomes 5% or more is not clear, it is rapidly dried at a high temperature so that the moisture content after drying becomes 5% or more. It is speculated that this may result in the formation of a structure that easily retains some kind of moisture.

[0020]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to the embodiments unless it exceeds the gist of the invention.

Examples 1 to 5 A spin dope in which cis-polybenzoxazole (PBO) having an intrinsic viscosity of 30 dl / g was dissolved in polyphosphoric acid at a concentration of 14% was added to 0.22 mm.
From a 334 nozzle having an orifice diameter of 160
It extruded at a single-hole discharge rate of 0.122 cc at ℃. The fibrous dope extruded from the nozzle passes through a 22 cm air gap, in which it is pulled, passes through a coagulation bath adjusted to about 22 ° C., and further travels at a speed of about 200 m / m.
The sample was washed continuously with 5 pairs of rollers in the water, and then continuously dried without being wound once by the following drying process.

Three drying rollers are used for drying (temperature 1, temperature 2, and temperature 3 in this order), and the temperature and residence time of each roller are changed so that the water content after the drying step becomes 5% or more. Fiber. The results are shown in Table 1. The residence time of each drying roller was about 15 seconds, and the residence time was adjusted by changing the number of rollers used. The obtained fiber was at a temperature of 2
The sample was allowed to stand at 0 ° C. and a humidity of 65%, and the change in weight was observed.

A plain woven fabric having a basis weight of 350 g / m ² was obtained from the obtained fibers by a known method. The carbonized length of the obtained fabric was measured in a combustion test according to JIS L1091, A-4 method, and heat resistance and flame resistance were compared. However, the flame contact time was changed from 12 seconds to 120 seconds. In addition, the pretreatment of the sample was performed only at a temperature of 20 ° C. and a humidity of 65% for 24 hours. The results are shown in Table 1.

[Examples 6 and 7] 20% of polybenzoxazole fiber and 80% of Nomex were obtained from the raw cotton having a cut length of 42 mm obtained from the fiber of Example 1 and the raw cotton having a cut length of 47 mm of Nomex, which is a meta-aramid fiber. Example 6) and a 20th spun yarn having 70% polybenzoxazole fiber and 30% Nomex (Example 7) were obtained by a conventional method. A plain woven fabric having a basis weight of 250 g / m ² was obtained using this fiber. A combustion test was performed in the same manner as in Example 1.

"Comparative Examples 1 to 5" Fibers were produced in the same manner as in Example 1, but the drying conditions were changed from those recommended in this patent as shown in Table 1 to obtain an equilibrium moisture content of 5%. Less fiber was obtained. Further, a fabric similar to that of the example was prepared, and its heat resistance and flame resistance were evaluated.

[0026]

[Table 1]

As is apparent from Table 1, the fabric having an equilibrium moisture content in the range of the present invention shows good heat and flame resistance.

[0028]

According to the present invention, by setting the equilibrium water content of the polybenzazole fiber to 5% or more, heat resistance and
A fabric having excellent flame resistance can be obtained.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) D03D 15/12 D01F 6/74

Claims (3)

(57) [Claims] 1. A heat- and flame-resistant fabric, wherein at least a part of a fiber made of a polybenzazole polymer is used, wherein the fiber has a substantially equilibrium moisture content of 5% or more. 2. The heat- and flame-resistant fabric according to claim 1, wherein the weight fraction of the polybenzazole fiber is 50% or more. 3. The heat-resistant and flame-resistant fabric according to claim 1, wherein the weight fraction of the polybenzazole fiber is 80% or more.