JPH0284532A - Production of flame-retardant fiber - Google Patents

Abstract

PURPOSE:To obtain the title fiber capable of enduring to processing of card hanging, etc., by introducing crosslinkage to an acrylic fiber, then introducing specific amounts of carboxyl group and amide group thereto by hydrolysis reaction and further forming crosslinking of a polyvalent metal ion. CONSTITUTION:Crosslinkage is introduced to an acrylic fiber consisting of acrylonitrile based polymer using hydrazine, hydroxylamine, etc., to control residual amount of nitrile group to 1.5-7mm mol/g. Then the fiber is immersed into a basic aqueous solution of alkali metal hydroxide, ammonia, etc., or aqueous solution of a mineral acid such as nitric acid or sulfuric acid and subjected to hydrolysis reaction by heat treatment to introduce 1.0-4.5mm mol/g carboxylic group and amide group of the residual amount. Further, crosslink of a polyvalent metal ion is formed by treating the fiber with an aqueous solution of zinc chloride, etc., to provide the aimed fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an industrial method for producing highly flame-retardant fibers that have a low degree of swelling and have practical performance that can withstand processing such as carding.

(Conventional techniques and problems) Conventionally, many methods have been proposed to obtain flame-retardant fibers, and one method involves attaching and fixing flame retardants such as phosphorus compounds and herogen compounds to the fiber surface. Although there are processing methods, these methods generally have various drawbacks such as durability, change in texture, and toxicity of the fuel itself and combustion.

Another typical example is a method of forming fibers using a polymer copolymerized with halogenated monomers such as vinyl halides and vinylidene halides, but highly flame-retardant fibers can be obtained by this method. In order to achieve this, it is necessary to copolymerize a large amount of halogenated monomer, and as a result, there are also essential drawbacks such as generation of toxic gas during combustion.

(Problems to be Solved by the Invention) The object of the present invention is to provide a highly flame-retardant material that does not have the above-mentioned essential drawbacks such as durability and toxicity during combustion, and has practical performance that can withstand processing such as card hanging. The object of the present invention is to provide a means for industrially producing fibers.

(Means for Solving the Problems) The above-mentioned object of the present invention is to introduce crosslinking into acrylic fibers to reduce the amount of residual nitrile groups from 1.5 to 'Immol/g.
After adjusting to within the range of 1.0 to 4 by hydrolysis reaction
．． By introducing 5 mmol/y of carboxyl groups and the remaining amide groups, and then forming polyvalent metal ion crosslinks, the acrylic fibers were filled into a container equipped with a pump circulation system, and the above-mentioned This can be achieved industrially advantageously by sequentially performing the introduction of crosslinks, the hydrolysis reaction, and the formation of polyvalent metal ion crosslinks.

The starting acrylic fiber was acrylonitrile (hereinafter referred to as AN
It is a fiber formed from an AN-based polymer containing 40% or more, preferably 50% or more of short fibers,
It may be in any form such as tow or nonwoven fabric, or may be a product in the middle of the manufacturing process, waste fiber, or the like.

AN-based polymers include AN homopolymer, AN and other seven polymers.
Other copolymers include vinyl halides and vinylidene halides: (meth)acrylic acid copolymers: methallylsulfonic acid, p-
Sulfonic acid-containing monomers such as styrene sulfonic acid and salts thereof: (Carboxylic acid-containing monomers such as methane acrylic acid and itaconic acid, and salts thereof; other monomers such as niacrylamide, styrene, and vinyl acetate).

There are no limitations on the method of introducing crosslinks into acrylic fibers, and any method can be used as long as the amount of residual nitrile groups can be adjusted within the range of 1.5 to 7 mmol/y. It is industrially preferable to use a method of treating at 50 to 120° C. for 1 to 5 hours. Note that if the amount of residual nitrile groups is less than the above lower limit, it will not be possible to produce the desired highly flame-retardant fiber, and if it exceeds the upper limit, it will not be possible to finally obtain a fiber with practically satisfactory physical properties. do not have.

In addition, the nitrile group is substantially eliminated by a hydrolysis reaction, and 1.0 to 4.5 mmol/g, preferably 1.5 to
A method for introducing a carboxyl group of 3.5 m mal / f and an amide group into the remainder is to use a basic aqueous solution such as an alkali metal salt or ammonia, or a water-soluble surface of a mineral acid such as nitric acid, sulfuric acid, or hydrochloric acid. Examples include impregnation, or heating treatment while the raw fiber is immersed in the aqueous solution.

In addition, if the carboxyl group is less than the above lower limit,
ultimately unable to provide a high degree of g1 flammability fiber,
Moreover, if the upper limit is exceeded, practically satisfactory physical properties cannot be obtained.

Ionic crosslinking methods include Zn, Cu, Ca, Fe
It is desirable to treat with a 1 to 20% by weight aqueous solution of a salt of a polyvalent metal such as Zn at a temperature of 1 O-too'c. The amount of polyvalent metal introduced through ionic crosslinking is as follows:
To achieve the purpose of the present invention, 0.5 to 8.5 m eq/9,
It is preferably within the range of 1.0 to 3.0 m eq/g.

In this way, the tensile strength is Ly/d or more, preferably 1.5 y/d or more, the water swelling degree is 100% or less, preferably 80% or less, and the limiting oxygen index (LOI) is 30 or more, preferably 32 or more flame retarding fibers can be produced industrially.

In addition, acrylic u1. A method of filling m into a container equipped with a pump circulation system and sequentially performing the above-mentioned cross-linking introduction, hydrolysis reaction, and formation of polyvalent metal ion cross-links is advantageous in terms of equipment, safety, and uniformity. Desirable from various points such as reactivity. A typical example of such a device (vessel equipped with a pump circulation system) is an Obermeyer dyeing machine.

In addition, we have introduced a predetermined amount of carboxyl groups and polyvalent metal ion crosslinks while maintaining fiber properties that do not pose any practical problems and suppressing water swelling as much as possible, providing fibers with a high degree of flame retardancy. In order to achieve this, it is particularly desirable to employ starting acrylic fibers having the following properties.

That is, acrylic fibers are selected in which the AN-based polymer molecules forming the fibers are sufficiently oriented and the dichroism ratio of Conco Red (hereinafter referred to as CR) is 0.4 or more, more preferably 0.5 or more. It is desirable to do so. In addition, the CR dichroism ratio is
It was determined according to the method described in Polymer Science 23 (252) 193 (1966).

In addition, it will take a while! There is no limitation on the means for producing J yv type woven fibers, and as long as the above CR dichroic ratio is satisfied, any known means can be used as appropriate.
at least 8 times, preferably at least 8 times, and the process shrinkage rate is 3 times or more.
By employing means to reduce the amount to 0% or less, preferably 20% or less, desired acrylic fibers can be manufactured with industrial advantage.

Furthermore, as a starting acrylic fiber, a fiber M (a spinning dope of an AN polymer is spun according to a conventional method, drawn and oriented, and has not been subjected to heat treatment such as dry densification or moist heat relaxation treatment) is used as the starting acrylic fiber. Fibers, especially wet or dry/wet spinning;
Water swelling itW gelatinous fiber after stretching: Internal moisture content 30-15
By using 0%), the dispersibility of the fibers in the reaction solution, the permeability of the reaction solution into the fibers, etc. are adjusted in several ways, and the introduction of crosslinking bonds and the hydrolysis reaction can be performed uniformly and quickly. This is desirable because it allows

(Effects of the invention) With the advent of the present invention, there are no problems such as durability of flame retardant performance or toxicity during combustion, the fiber properties are maintained without any practical problems, and the degree of water swelling is suppressed to below a certain level. A characteristic advantage of the present invention is that it provides an industrially advantageous means for producing fibers that are highly flame retardant and have a high degree of flame retardancy.

The flame-retardant fibers obtained in this manner are widely used in any application form requiring a high degree of flame retardancy.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples. Parts and percentages in the examples are expressed on a weight basis unless otherwise specified.

In addition, residual nitrile group amount (mmO/'/g), carboxyl group amount (m mol/I) Polyvalent metal introduction i
(-m eq /y), water swelling degree (%) and LOIi
, was determined by the following method.

(1) Amount of residual ditolyl group (m
rno#/f) AN7 methyl acrylate (
MA) ratio is 10010.80/20.50150.
From the IR spectrum of the 30/7010/90 polymer, calculate the absorbance at the absorption peak of the nitrile group to create a calibration curve, and based on this, calculate the amount of nitrile groups remaining after the introduction of crosslinking from the IR spectrum of the test fiber. was calculated.

Group (2) Carboxyl drag amount (m mol / f)
Precisely weigh approximately Iy of sufficiently dried test fibers (Xfl), add 200 #I10 water to this, add IN hydrochloric acid aqueous solution while heating to 50°C to make I)H2, then O
, l N fj A titration curve was determined using an aqueous soda solution according to a conventional method. The amount of caustic soda aqueous solution consumed by carboxyl groups (Ycc) was determined from the titration curve. From the above measurement results, it was calculated using the following formula.

0, 1 Y (Amount of carboxyl group) - If polyvalent cations are included, it is necessary to determine the amount of these cations by a conventional method and correct the above formula.

(3) Amount of polyvalent metal introduced (meq/9) Determined by elemental analysis.

(4) Degree of water swelling (shadow) Approximately 0.4 y of the test fiber was placed in 300 liters of pure water at 25°C.
After immersion for 0 minutes, centrifugal dehydration at 100G x 3 minutes (G is gravitational acceleration) and the adjusted weight of the sample was measured (Vhy).
Next, the sample was dried in a vacuum dryer at 80° C. until it reached a constant weight, and the weight of the fiber was measured (W2y) and calculated using the following formula.

(5) LOI The measurement was carried out in accordance with the minimum oxygen index measurement method of JIS K7201.

Example 1 AN-based polymer consisting of 9Q% AN and 9% MAI (impact density [η1 in dimethylformamide at 30°C)
: 1.2) After spinning and stretching (total stretching ratio: 10 times) a spinning dope in which 10 parts were dissolved in 90 parts of a 48% Rodan soda aqueous solution, soft ball/wet ball = 120°C/6
Dry in an atmosphere at 0°C (process state 1 shrinkage rate 14%) to obtain raw fiber 1 with a single fiber fineness [,5d (CR dichroism ratio 0.58)
) was obtained.

1 kg of raw fiber 1 was packed into an Obermeyer dyeing machine (manufactured by Hikosaka Seisakusho, hydrazine hydra) 800y/#
(bath ratio l: 30, circulation flow rate 517 minutes) and treated at 100° C. for 3 hours. The amount of residual nitrile groups is 8.
It was 5 mmog/y.

Next, using ION sulfuric acid aqueous solution, 80°C x 8
A time immersion treatment (bath ratio 1:10, circulation flow 15e/min) was carried out. This fiber has virtually no nitrile groups,
2.13 mmol/f of carboxyl groups were introduced.

Next, using 14f of 5% zinc chloride aqueous solution, 2
Treated at 0°C for 30 minutes (bath ratio 1:10, circulation flow rate 5e
/min) A fiber medium was prepared.

The tensile strength in the fiber is 1.9y/d, the degree of water swelling is 50%,
The amount of Zn introduced was 2.1 m eq/9. L OI is 3
I failed at 4.

A comparative fiber was prepared in the same manner as in Fiber + I) except that an aqueous solution of 100 y/l of hydrazine hydrogen hydride was used and the remaining IJ/base amount was adjusted to 8.0 mmol/V. Fiber A4 was very brittle and had a tensile strength of 0.7 f/d.

Further, a comparative fiber IB) was produced in the same manner as in the fiber except that an aqueous solution of hydrazine hydra-tro 00y/# was used and the amount of residual nitrile groups was adjusted to 0.5 mmol/g.

Fiber (average had a tensile strength of 1.8 y/d, but L
OI was 25, which was insufficient.

Example 2 Raw material fiber 2 (CR dichroism ratio 0.55) was obtained in the same manner as in Example 1 except that vinylidene chloride was used instead of MA, and this was treated in the same manner as in Example 1 (residual nitrile groups were removed). Amount 3.
4 mmog/9) to produce fibers tl).

The amount of carboxyl groups in fiber 1) is 2.8 mmol/
f, tensile strength is 1.8y/d, water swelling degree is 30%, Zn
Introduced amount is 1.9 m eq / f, LOI is 37
Met.

Example 3 Raw material fiber 8 (CR dichroic ratio 056) was obtained in the same manner as in Example 1 except that vinyl acetate was used instead of MA.

This was treated in the same manner as in Example 1, except that the surface was changed to the ION sulfuric acid aqueous surface and treated with a 5% caustic soda aqueous solution at 95°C for 30 minutes (residual nitrile group amount: 3.5 m mal! /
f) Fibers (ribs) were prepared.

The tensile strength of fiber l1l) is 1.7 f/d, and the degree of water swelling is 6.
0%, CI3 introduction amount is 2゜3 m eq / 9,
LOI was 83.

Claims (1)

[Claims] 1. After introducing crosslinking into the acrylic fiber and adjusting the amount of residual nitrile groups within the range of 1.5 to 7 mmol/g,
A method for producing flame-retardant fibers, which comprises introducing 1.0 to 4.5 mmol/g of carboxyl groups and the remainder amide groups through a hydrolysis reaction, and then forming polyvalent metal ion crosslinks. 2. Claim 1, characterized in that the acrylic fibers are filled in a container equipped with a pump circulation system, and the introduction of crosslinks, hydrolysis reaction, and formation of polyvalent metal ion crosslinks are performed sequentially.
The method for producing the flame-retardant fiber described.