JPH0364526A - Production of sulfur-containing acrylic flameproof yarn - Google Patents

Abstract

PURPOSE:To uniformly carry out reaction in obtaining flameproof yarn heating and sulfurizing yarn bundle of acrylic fiber in a sulfur-containing atmosphere, by replacing oxygen in the yarn bundle with water, etc., through immersion of the yarn bundle in water at an inlet part of heating furnace. CONSTITUTION:Yarn bundle 1 of acrylic fiber (preferably one having >=10g/d tensile strength, >=180g/d modulus in tension and >=2.2g/d knot strength) which is obtained by subjecting acrylonitrile (preferably one having high degree of polymerization of 2.0-5.0 intrinsic viscosity) to melt spinning and drawing is immersed in water at an inlet part 2, brought into contact with steam 3, heated by a furnace 4, sulfurized with a high-temperature sulfur-containing gas (preferably mixed gas of sulfur dioxide and steam at 230-400 deg.C) and preferably brought into contact with steam 3 at an outlet part 6 to give sulfur-containing acrylic flame-retardant yarn suitable for cement reinforcing material, etc., having high tensile strength, excellent alkali resistance, heat resistance and flame retardance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a sulfur-containing acrylic flame-resistant fiber that has high tensile strength and excellent alkali resistance, heat resistance, and flame resistance.

[Prior Art] Conventionally, protective equipment such as firefighting suits, furnace vests, and welding spark protection sheets, sealing materials such as gaskets and ground backings, insulation materials, and filter media represented by bag filters,
Asbestos has been widely used in products that require heat resistance and flame resistance, such as friction materials such as brakes and clutches, and electrical insulation materials.

Furthermore, asbestos has excellent alkali resistance at high temperatures, and asbestos cement boards and calcium silicate boards, etc.
It is also used in large quantities in high-performance hydraulic inorganic products made of calcareous or silica materials that are autoclaved in steam at 80°C.

However, in Japan, which relies on imports for most of its asbestos, in addition to the problem that the manufacturing cost of products fluctuates greatly depending on the import price of asbestos, in recent years the asbestos dust has seriously harmed the health of workers. As a result, its use has been legally regulated in the United States and some European countries, and the development of textile materials to replace asbestos is being researched and considered on a global scale, including in Japan. .

Various fibers have been proposed to replace asbestos, such as glass, rock wool, carbon fiber, phenol fiber, steel fiber, aramid fiber, and flame-resistant fiber. Flame-resistant fibers that are small in size, flexible, have excellent flame retardancy, and are cheaper than carbon fibers, ie, acrylic flame-resistant fibers, are attracting the most attention.

However, flame-resistant fibers produced by heating and oxidizing acrylic fibers in high-temperature air have a non-uniform oxidation structure in which the degree of oxidation on the surface of the fibers is generally greater than on the inside of the fibers. have.

For this reason, mechanical strength, particularly tensile strength and knot strength, is low and toughness is low, making spinning or knitting difficult.

Furthermore, even if spinning, knitting, and weaving were possible, the resulting product would have poor abrasion resistance and heat resistance, and if used for a long time at high temperatures of 150°C or higher, its strength would decrease and practical performance would be lost. was there.

Furthermore, flame-resistant fibers obtained by heating and oxidizing the above-mentioned acrylic fibers in the air have significantly poor alkali resistance at high temperatures.
It cannot be used at all as a reinforcing material for hydraulic inorganic products that are autoclaved in steam at 180°C.

Therefore, the present inventors first heated and sulfurized high-strength acrylic fibers in a sulfur-containing atmosphere such as sulfur dioxide, thereby achieving high tensile strength and toughness.
We proposed a sulfur-containing acrylic flame-resistant fiber that has excellent alkali resistance, heat resistance, flame resistance, and chemical resistance at high temperatures.

Also, special public ff? Publication No. 147-24967 describes a special method for continuously obtaining carbon fibers that involves keeping the pressure in the heat treatment chamber slightly lower than atmospheric pressure when heat treating acrylic fibers in a sulfur dioxide gas atmosphere to make them flame resistant. discloses a method for preventing the leakage of sulfur dioxide gas from an inlet/outlet portion.

[Problems to be Solved by the Invention] Carbon fibers are generally produced by heating and oxidizing acrylic fibers in an oxidizing atmosphere such as air in a flame-retardant process, and then carbonizing them in a high-temperature non-oxidizing atmosphere. Manufactured by Therefore, even if oxygen or air is mixed into the sulfur-containing gas during the flameproofing process as described in the above-mentioned known example, there is no problem in obtaining carbon fibers.

However, when using acrylic fibers as flame-retardant fibers that have undergone only a flame-retardant process, heating and oxidizing the acrylic fibers in the air will significantly reduce the performance of the flame-retardant fibers, so It is desirable to minimize the amount of air, ie, oxygen, mixed in.

An object of the present invention is to provide a method for producing sulfur-containing acrylic flame-resistant fibers (hereinafter simply referred to as flame-resistant fibers) that have high tensile strength and excellent alkali resistance, heat resistance, and flame resistance at high temperatures. .

As a result of intensive studies to achieve this objective, the present inventors have discovered that sulfur-containing acrylic flame-resistant fibers obtained by continuously heating and sulfurizing fiber bundles made of acrylic fibers in a sulfur-containing atmosphere. The present invention was developed based on the prospect that the sulfurization reaction between the sulfur-containing gas and the acrylic fibers could be promoted by suppressing as much as possible the flow of air, that is, oxygen, accompanying the fiber bundle into the sulfur-containing atmosphere during production. It was completed.

[Means to solve the problem] The present invention has the following configuration.

(1) When obtaining flame-resistant fibers by continuously heating and sulfurizing fiber bundles made of acrylic fibers in a sulfur-containing atmosphere,
A method for producing sulfur-containing acrylic flame-resistant fibers, which comprises immersing the fiber bundle in water or bringing it into contact with steam at least at the entrance of a heating furnace.

(2) The sulfur-containing acrylic flame-resistant fiber according to (1), wherein the sulfur-containing atmosphere is at least one sulfur-containing gas selected from sulfur dioxide, sulfur gas, carbon disulfide, hydrogen sulfide, and carbonyl sulfide. Production method.

(3) The method for producing a sulfur-containing acrylic flame-resistant fiber according to (1) or (2), wherein the sulfur-containing atmosphere is a mixed gas of a sulfur-containing gas and an inert gas.

(4) The inert gas is at least one selected from nitrogen, argon, helium, carbon dioxide, and water vapor (3
) The method for producing a sulfur-containing acrylic flame-resistant fiber.

The present invention will be explained in detail below.

The sulfur-containing atmosphere used in the present invention refers to a sulfur-containing gas consisting of sulfur dioxide, sulfur gas, carbon disulfide, hydrogen sulfide, carbonyl sulfide, etc. alone or a mixture thereof, or a mixture of the above sulfur-containing gas and an inert gas. Among gases, sulfur dioxide is particularly preferably used because it has excellent reactivity with acrylic fibers and can uniformly sulfurize the cross section of the fibers.

The inert gas is a gas that does not cause a chemical reaction with the acrylic fibers, such as nitrogen, argon, helium, carbon dioxide, water vapor, or a mixture thereof.

By the way, fiber bundles made of acrylic fibers are immersed in water or brought into contact with steam and then introduced into the heating furnace for the next process.At this time, water vapor is present in the heating furnace accompanying the fiber bundles. Inflow.

Therefore, the sulfur-containing atmosphere is preferably a mixed gas of sulfur-containing gas and water vapor. Furthermore, when water vapor is used as an inert gas in this way, when recovering sulfur-containing gas from the waste gas after the sulfurization reaction between acrylic fibers and sulfur-containing gas, the water vapor is separated as water and then dissolved in the water. Sulfur-containing gas can be easily recovered by fractional distillation. Moreover, the collection equipment can be downsized, which is extremely advantageous in reducing collection costs.

Here, the content of the sulfur-containing gas in the sulfur-containing mixed gas is 3 mol% or more, preferably 5 mol% or more. If the content of the sulfur-containing gas is less than 3 mol%, thermal deterioration precedes the sulfurization reaction between the acrylic fiber and the sulfur-containing gas, making it impossible to obtain high-performance flame-resistant fibers.

In addition, the oxygen content contained in the sulfur-containing atmosphere is 1-
It is preferably 0.5 mol% or less, more preferably 0.1 mol% or less.

When the oxygen content exceeds 1 mol%, the sulfurization reaction between the acrylic fiber and the sulfur-containing gas is preceded by an oxygen reaction, which may cause molecular chain scission, give a non-uniform oxidation structure to the fiber cross section, or cause sulfur Unless the formation of a cyclized structure and a crosslinked structure containing bonds is inhibited, it becomes impossible to obtain a high-performance flame-resistant fiber.

Next, the acrylic fibers used in the present invention are not particularly limited, but in order to obtain flame-resistant fibers with high tensile strength and excellent toughness, acrylic fibers are also used with high strength and high elasticity. It is desirable that the rate is high. For example, the degree of polymerization is at least 1. 5, preferably 2
．． Acrylonitrile with a high polymerization degree of 0 to 560 (hereinafter referred to as AN
) type polymer with a tensile strength of at least 7g
/d.

It is desirable to form acrylic fibers preferably at least 9 g/d, more preferably at least 10 g/d.

Here, the ΔN polymer used in the production of acrylic fibers includes AN alone or at least 90 mol% of AN.
and 10 mol% or less of a monomer copolymerizable with the AN, such as carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, and lower alkyl esters thereof;
Hydroxyalkyl acrylate containing a carboxylic acid hydroxyl group such as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxymethyl methacrylate-1, acrylamide, methacrylamide, α-chloroacrylonitrile, hydroxyethyl acrylic acid,
Copolymerized monomers such as allylsulfonic acid and methacrylsulfonic acid can be exemplified, but among these copolymerized monomers, sulfurization reaction is fast, oxidative deterioration due to oxygen is small, and flame-resistant fibers with high strength can be obtained. Acrylamides are particularly preferred.

These AN-based polymers are dimethyl sulfoxide (DMS
O), organic solvents such as dimethylformamide (DMF) and dimethylacetamide (DMAc), concentrated aqueous solutions of inorganic salts such as calcium chloride, zinc chloride, and rhodan soda;
When dissolved in an inorganic solvent such as nitric acid, the solution viscosity is 2000.
Poise or more, preferably 3000 to 1000 boise,
A spinning dope having a polymer concentration of 5 to 20% is prepared.

In order to produce dense fibers with as high strength and high modulus as possible and with little difference in internal and external structures from the solvent solution (spinning stock solution) of the high polymerization degree AN polymer thus obtained, it is necessary to use this high polymerization degree AN polymer. A so-called dry-wet spinning method is adopted, in which the polymer spinning solution is once discharged into an inert atmosphere such as air through a spinneret, and then the discharged spinning solution is introduced into a coagulation chamber to complete coagulation. It is desirable to do so.

The specific conditions for this wet-dry spinning are such that the distance between the spinneret surface and the coagulation bath liquid level is 1 to 20 mm.
After the spinneret is discharged into a microspace formed by the spinneret surface and the coagulation bath liquid level, which is preferably set within a range of 3 to 1Q mm, it is introduced into a coagulation bath and coagulated, and then the obtained fiber thread is By conventional methods, the fibers are subjected to post-processing steps such as water washing, solvent removal, primary stretching, drying/densification, secondary stretching, and heat treatment to form drawn fiber threads. The fiber yarn obtained by this dry-wet spinning has extremely excellent drawability, but preferably the secondary drawing method is at least 1.1 times, preferably 1.5 times, under dry heat at 150 to 270°C. or more, the total effective stretching ratio is at least 10 times, preferably 12 times or more, and the fineness is 0.5 to 7 deniers (
d), preferably within the range of 1 to 5d.

If the fineness is smaller than 0.5d, the spinnability of the resulting flame-resistant fiber will be reduced, making it difficult to obtain textile products with good abrasion resistance.If the fineness is larger than 7d, the fiber cross section will This is not preferable because the sulfurization becomes uneven.

2 The fiber thus obtained usually has mechanical properties such as a tensile strength of 7 g/d or more and a tensile modulus of 130 g/d or more, but is more preferably made of a highly polymerized AN-based polymer with an intrinsic viscosity of 2.5 or more. It is preferable to use fibers having mechanical properties such as a tensile strength of 10 g/d or more, a tensile modulus of 180 g/d or more, and a knot strength of 2.2 g/d or more.

Next, a method of continuously heating and sulfurizing a fiber bundle made of acrylic fibers according to the present invention will be explained with reference to FIG.

In FIG. 1, a fiber bundle 1 made of acrylic fibers advances in the direction of arrow A. The fiber bundle 1 is brought into contact with water vapor 3 at the inlet 2 . Here, the air accompanying the fiber bundle 1 is replaced by water vapor 3. The fiber bundle 1 is then introduced into a heating furnace 4 and sulfided by heated sulfur-containing gas 5, and then brought into contact with steam 3 again at an outlet section 6 and wound up.

At this time, the sulfur-containing gas accompanying the fiber bundle 1 is replaced by the water vapor 3 in the outlet section 6.

Although the fiber bundle 1 is brought into contact with water vapor at both the inlet and the outlet 30, contact may be made only at the inlet of the heating furnace, and in this case, the outlet may be sealed with an inert gas or the like. .

The key point is that the air accompanying the fiber bundle, that is, oxygen, is replaced with water or steam at the inlet of the heating furnace, so that the fiber bundle is continuously heated and sulfurized in a sulfur-containing atmosphere, resulting in less oxidative deterioration due to oxygen and sulfur-containing fibers. All that is required is for the gas reaction to proceed smoothly and uniformly across the fiber cross section.

Furthermore, the temperature of the sulfur-containing gas in the sulfur-containing atmosphere is 2
The heating temperature in the sulfurization process may be from 30 to 400°C, and may be at a constant temperature or at an elevated temperature, and the acrylic fiber bundle may be under tension, constant length, or relaxed. −
As an example, the first stage heating is performed in a heating furnace maintained at a temperature range of 230 to 280 °C, and the second stage heating is performed at a temperature range of 280 to 400 °C.
A method of completing the sulfurization in a heating furnace within a temperature range of 0.degree. C. and in which temperature raising conditions are set in stages can be mentioned.

The thus obtained flame-resistant fiber of the present invention has a sulfur content of at least 0. 5% by weight, preferably 1-2
0% by weight, and the tensile strength is 3.5 g/d or more, preferably 4.0 g/d or more, more preferably 5.0 g/d or more.

The sulfur-containing acrylic flame-resistant fiber obtained by the present invention can be widely used as an asbestos substitute fiber, such as autoclave curing cement reinforcing materials, friction materials, ground backing, sealing materials such as gaskets, firefighting suits, and welding spark protection sheets. , this industrial significance is extremely large.

Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples.

[Example] In the present invention, tensile strength and intrinsic viscosity are values measured by the following measuring method.

(1) Tensile strength: Measured according to the measuring method specified in J I 5-L-1069.

(2) Intrinsic viscosity: 75 mg of dry AN polymer was placed in a flask, and DM containing 0.1N sodium thiocyanate was added.
Add 25 mg of F and dissolve completely. The specific viscosity of the obtained polymer solution was measured at 20° C. using an Ostwald viscometer, and the intrinsic viscosity was calculated according to the following formula.

Intrinsic viscosity [1+1.32X >, 1 ) -1] 10.19
8 Example 1 2 mol% acrylamide, 98 mol% A, N in DM
Solution polymerization was carried out in SO to produce an AN polymer having an intrinsic viscosity of about 3.0. The obtained AN-based polymer solution was used as a spinning stock solution, and wet-dry spinning was performed. As a coagulation bath, 15°C, 55°C
% DMSO aqueous solution was used. Further, the distance between the spinneret and the coagulation bath liquid level was set to 5 mm, and the distance from the coagulation bath liquid level to the focusing guide was 400 mm.

The obtained undrawn fiber yarn was drawn 5 times in a hot water bath, then an oil agent was applied thereto, and it was dried and densified at 11-0°C.

Then, in a dry heat tube at 180°C, the highest stretching ratio was 85.
% to obtain an acrylic fiber bundle with a single fiber fineness of about 2 deniers, a tensile strength of 14 g/d, and a filament size of several 6,000.

This fiber bundle was fed into a pipe filled with water vapor to replace the air in the fiber bundle with water vapor, and then heated at 280°C in a sulfur-containing mixed gas consisting of 20% sulfur dioxide and 80% water vapor.
It was heated and sulfurized for 30 minutes.゛At this time, the oxygen content in the sulfur-containing atmosphere was 0.06%.

The obtained flame-resistant fiber had a sulfur content of 2.5% by weight and a tensile strength of 10 g/d. As a result, in the present invention, flame-resistant fibers with high tensile strength were obtained because there was little deterioration due to oxygen and the reaction with sulfur dioxide proceeded smoothly.

C Effect of the invention] The present invention provides a method for immersing a fiber bundle made of acrylic fibers in water or contacting it in water vapor to replace the air, that is, oxygen accompanying the fiber bundle, with water or water vapor, and then removing the fiber bundle from a sulfur-containing atmosphere. Since the fiber is continuously heated and sulfurized inside, there is little oxidative deterioration caused by oxygen, and the reaction caused by the sulfur-containing gas proceeds smoothly and uniformly across the cross section of the fiber.

Therefore, the flame-resistant fibers obtained not only have high tensile strength but also
Excellent alkali resistance, heat resistance, and flame resistance at high temperatures.

[Brief explanation of drawings]

The first factor is an explanatory diagram showing an example of an embodiment in which a fiber bundle made of acrylic fibers according to the present invention is continuously heated and sulfurized. 4: Heating furnace 5: Sulfur-containing gas 6: Outlet part

Claims (4)

[Claims] (1) When obtaining flame-resistant fibers by continuously heating and sulfurizing fiber bundles made of acrylic fibers in a sulfur-containing atmosphere,
A method for producing sulfur-containing acrylic flame-resistant fibers, which comprises immersing the fiber bundle in water or bringing it into contact with steam at least at the entrance of a heating furnace. (2) The sulfur-containing acrylic flame-retardant according to claim 1, wherein the sulfur-containing atmosphere is at least one sulfur-containing gas selected from sulfur dioxide, sulfur gas, carbon disulfide, hydrogen sulfide, and carbonyl sulfide. Fiber manufacturing method. (3) The method for producing a sulfur-containing acrylic flame-resistant fiber according to claim 1 or 2, wherein the sulfur-containing atmosphere is a mixed gas of a sulfur-containing gas and an inert gas. (4) The method for producing a sulfur-containing acrylic flame-resistant fiber according to claim (3), wherein the inert gas is at least one selected from nitrogen, argon, helium, carbon dioxide, and water vapor.