JPS6233824A - Acrylic flameproofed fiber having improved abrasion resistance - Google Patents

Abstract

PURPOSE:The titled fibers, consisting of oxidized fibers having a specific value of tensile strength and fiber knot strength and a given value or above of limit oxygen index, having improved heat resistance and flame resistance and further usefulness as asbestos substitute fibers and rich in practicality. CONSTITUTION:Acrylic flameproofed fibers obtained by oxidizing ultrahigh- strength fibers having 1.5-4.5g/denier tensile strength and >=1g fiber knot strength in an oxidizing atmosphere, e.g. air, while heating and converting the fibers into oxidized fibers having >=35 limit oxygen index (LOI). The above- mentioned acrylic flameproofed fibers are preferably oxidized fibers prepared from acrylic fibers having >=10g/denier tensile strength and >=2.2g/denier knot strength and obtained by dry-jet and wet spinning as a precursor.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention has excellent heat resistance and flame resistance, and its mechanical strength, especially abrasion resistance, greatly exceeds that of conventional acrylic oxidized fibers. Regarding acrylic flame resistant fibers.

(Conventional technology) Conventionally, protective equipment such as firefighting suits, furnace vests, welding spark prevention sheets, sealing materials such as gaskets and gland packings,
Asbestos is widely used in applications that require heat resistance and flame resistance, such as heat insulation materials, filter media such as bag filters, friction materials such as brakes and clutches, and electrical insulation materials.

However, most of this asbestos is imported, so not only does the manufacturing cost fluctuate due to price fluctuations, but in recent years it has become clear that asbestos dust can seriously impede the health of workers. There is a strong demand for materials to replace asbestos, and many fibers have been proposed as such alternative fibers, such as glass, rock wool, carbon fibers, phenolic fibers, steel fibers, aramid fibers, and flame-resistant or oxidized fibers. .

Among these asbestos alternative fibers, acrylic flame-resistant fibers,
In other words, oxidized fiber obtained as an intermediate product in the production of carbon fiber is attracting the most attention because it has a low specific gravity, is flexible, has flame retardant properties, and is significantly cheaper to manufacture than carbon fiber. It is one of the asbestos alternative fibers.

However, because conventional flame-resistant acrylic fibers have low mechanical strength, especially single fiber knot strength, they are difficult to spin, knit and weave like ordinary fibers, and the resulting fabrics It has been said that this material has poor wear resistance and lacks practical performance.

As an acrylic flame-resistant fiber that has improved this drawback, Jibun Sho 59-76927 discloses that precursor acrylic fibers were treated with an aqueous solution containing a small amount of e and P compounds, heated in air. , by oxidizing 1
Oxidized fibers for producing fibrous activated carbon with a critical oxygen index (IOI) of 45 or more and high elongation have been proposed.

However, although this flame-resistant acrylic fiber has high elongation and is flexible, it has insufficient knot strength, and in terms of abrasion resistance, it is no different from fabrics made of conventional flame-resistant acrylic fibers. It didn't work.

(Problems to be Solved by the Invention) The purpose of the present invention is to greatly improve the abrasion resistance of the above-mentioned flame-resistant acrylic fibers, and to easily form 15 pieces using commonly used spinning, knitting and weaving techniques. The present invention also provides a highly practical acrylic flame-resistant fiber that is useful as an asbestos substitute fiber.

(Means for Solving the Problems) The object of the present invention is to achieve the invention described in the above claims, that is, a tensile strength of 1.5 to 4.5 g/d and a single Idi fiber nodule of at least 1Q. Strong limiting oxygen index (LOI) of 3
This can be achieved by using acrylic flame-resistant fibers made of oxidized fibers with an oxidation rate of 5 or more.

The flame-resistant acrylic fiber of the present invention is characterized by having a tensile strength of 1.5 to 4.5 C1/d and a tensile strength of 1.5 to 4.5 C1/d.
It has a single fiber knot strength of 0 or more. In other words, conventional flame-resistant acrylic fibers are known to have relatively high tensile strength, but have low knot strength.
When converting into thread-like products and textiles, for example, fluff is generated in the process of spinning and knitting, which not only makes it impossible to form good thread-like products and textiles, but also prevents the formation of good thread-like products and textiles. However, the fibers tend to wear out and fall off, resulting in a lack of durability, making them generally impractical.

The feature of the present invention is to improve the abrasion resistance of the acrylic flame-resistant fiber binding by greatly improving the single fiber knot strength, which was the biggest drawback of the conventional flame-resistant acrylic fiber. When the single fiber knot strength has a value of at least 1 g, troubles such as the occurrence of fluff during the manufacturing process of spun yarns and fabrics made of the above-mentioned flame-resistant fibers can be prevented, and the mechanical properties of the resulting fabrics can be significantly improved. The point is that we have found that it can be improved. here,
Acrylic flame-resistant fibers having a single fiber knot strength of at least 1 g cannot be obtained by conventional methods for producing flame-resistant acrylic fibers, but can only be obtained by applying the method detailed below. can.

However, the acrylic flame-resistant fiber specified in the present invention is
A high molecular weight acryloni-1-lyl polymer having an intrinsic viscosity of at least 2.5, preferably 3.0 or more is used as a precursor fiber, that is, a precursor, and this polymer solution is dried as a spinning dope. Fibers obtained by wet spinning, especially those with a tensile strength of at least 10
Q/d, nodule strength is 2. Using ultra-high strength fibers of I/D or higher, the ultra-high strength fibers are heated and oxidized in an oxidizing atmosphere such as air to convert them into acrylic flame-resistant fibers with a limiting oxygen index (LOI) of 35 or higher. for the first time)
I can do it.

Here, dry/wet spinning is not a spinning method in which a normal spinning dope is directly discharged through a spinneret into a coagulation bath and the discharged yarn is coagulated in the coagulation bath, but the spinning dope is discharged from the spinneret. This is a method in which the yarn is first introduced into a microscopic space filled with an inert atmosphere such as air, nitrogen, helium, or argon, and after traveling through this space, the discharged yarn is introduced into a coagulation bath and coagulated. Only by applying such a method can a high-strength polymer with a prememory limit viscosity of 2.5 or more be produced with a tensile strength of 100/d or more and a knot strength of 2.
．． Ultra-high strength acrylic fibers with a strength of 20/d or more can be obtained. Then, such ultra-high-strength acrylic fibers are used as acrylic flame-resistant fiber raw materials, that is, precursors, and the precursors have a limiting oxygen index (LOI) of 3.
When converted to an acrylic flame-resistant fiber with a rating of 5 or more, not only the tensile strength but also the single fiber knot strength increases by jq or more, preferably 1
．． This makes it possible to produce an acrylic flame-resistant fiber with extremely high single fiber knot strength compared to conventional ac-1-nor flame-resistant fibers of 50 or higher.

It is extremely important that the single fiber knot strength is 1 g or more when processing the acrylic flame-resistant fiber into flame-resistant spun yarn or flame-resistant fabric.
If it is smaller than g, no matter how high the tensile strength or elongation is, when processing into spun yarn or fabric, such as woven fabric, knitted fabric, or non-woven fabric, problems such as generation of fluff may occur. It is not possible to produce good quality spun yarns and fabrics, and the resulting spun yarns and fabrics have low abrasion resistance and do not substantially satisfy practical performance.

Further, in the present invention, the limiting oxygen index (LOI) of the acrylic flame-resistant fiber is 35 or more, preferably 45 to 70.
It is desirable that the range is within the range of this limit vL index L
OI) becomes smaller than 35, acrylic flame resistance R
The heat resistance or flame resistance of the fiber will be impaired, and if it is too large, the flexibility and bending resistance will decrease, which is not preferable.

Hereinafter, specific embodiments of the method for producing flame-resistant acrylic fibers of the present invention will be described.

First, acrylonitrile (hereinafter referred to as A
An acrylic fiber consisting of a single polymer (referred to as N) and/or a copolymer containing the AN as a main component and a vinyl compound having copolymerizability with the ΔN is used.

Here, the vinyl compound having copolymerizability with AN is not particularly limited, but includes, for example, dicarboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, and methyl acrylate and methyl methacrylate. Water of carboxylic acid such as lower alkyl ester, hydroxyedyl acrylate 1~, hydroxymethacrylate M! Examples include esters containing α-chloroacrylonitrile, hydroxyethyl acrylic acid, allylsulfonic acid, and methacrylsulfonic acid.

Further, in order to increase the mechanical strength of the acrylic fiber obtained from the AN-based polymer, the intrinsic viscosity of the ΔN-based polymer should be at least 2.5, preferably in the range of 3.0 to 5.0. is desirable.

This intrinsic viscosity is a value measured as follows.

Add 75 mCl of dry polymer to the flask and add 0.1
Add dimethylformamide (DMF>25 ml containing N sodium thiocyanate and dissolve completely. The resulting polymer solution was heated at 20'C using an Ostwald viscometer.
Measure the specific viscosity and use the following formula to save the intrinsic viscosity.

Intrinsic viscosity - The above AN-based polymer is
F), organic solvents such as dimethyl acetamide (DMAC), R-free concentrated solutions such as lucium chloride, zinc chloride, rhodan soda, and inorganic solvents such as nitric acid, preferably D
Dissolved in an organic solvent such as MSO, with a solution viscosity of at least 2.000 Bois, preferably from 3.000 to 10.0
The spinning stock solution has 00 voids and a polymer Q degree of 5 to 20%.

jq The raw spinning solution is spun by the above-mentioned wet spinning method. In this case, the distance between the spinneret surface and the liquid level of the coagulation bath depends on the type of solvent, viscosity, and polymer concentration of the spinning solution. It is usually set in the range of 1 to 20 mm, preferably 3 to 1 Qmm, although it varies depending on the factors.

As the coagulation bath, an aqueous solution of the same solvent as the solvent of the polymer is used, and the fiber threads that have been coagulated in this coagulation bath are washed in hot water and desolvated, while the primary concentration is increased 2 to 10 times. Stretched. - After the next drawing, the water-swollen fiber yarn is dried and densified in a heated atmosphere, and then heated to 150-270'C
secondary stretching to at least 1.1 times, preferably 1.5 times or more under dry heat in a temperature range of
The fiber yarn is drawn 0 times, preferably 12 times or more.

The acrylic fiber precurly obtained in this way exhibits a high degree of crystal orientation with an X-ray crystal orientation of 93% or more, a tensile strength of at least 10 C]/d, a tensile modulus of at least 180 g/d, and a knot strength. It is an ultra-high strength fiber that is dense with a coefficient of 2.2Ω/d or more and smooth without surface defects, that is, with a coefficient of static friction of at least 0.3, and has physical properties and structural properties not found in conventional acrylic fibers. Has characteristics.

This structural feature that the coefficient of static friction is 0.3 or more is due to the fact that the acrylic flame-resistant fiber of the present invention uses 1 g of acrylic fiber obtained by the above-mentioned wet spinning as a precursor. It is denser and smoother than conventional acrylic flame-resistant fibers.

Further, it is desirable that the single fiber fineness of 1 g of the acrylic fiber precursor is in the range of 0.5 to 7 denier (d), preferably 1 to 5 d. In other words, the single fiber fineness is 0.
．． If it is smaller than 56, the spinnability of the resulting flame-resistant fiber will decrease and it will be difficult to make an acrylic flame-resistant fabric with good abrasion resistance. This is undesirable because oxidation becomes significantly uneven in the cross-sectional direction of the fibers, resulting in a decrease in single fiber knot strength.

The acrylic fiber precursor, which has such excellent physical properties and unique structure, can be heated in an oxidizing atmosphere.
Although it is oxidized, the oxidizing atmosphere is 200 to 350
Oxidized in air or an oxidizing gas such as SO2, preferably 302 gas, within the temperature range of 'C.

In this oxidation step, the oxidation temperature may be constant or elevated, but the precursor has a limiting oxygen index (LOI) of 35 or more, preferably in the range of 45 to 70, under tension or relaxation. It is best to heat and oxidize.

More specifically, the atmospheric temperature of the first oxidation furnace is set to 200~200℃.
Set the temperature to 240℃ and start oxidation, 250-35℃
Oxidation is preferably carried out in an oxidation furnace in which the temperature is raised stepwise in the temperature range of 0°C.

Due to the large fineness of the single fibers mentioned above, uniform oxidation is difficult.
When oxidation requires a long time, the acrylic fiber precursor or LOI is 21 to 35, preferably 23 to 3.
A compound having the ability to promote dehydration oxidation, such as L ammonium borate, borax, orthophosphoric acid, condensed phosphoric acid, ammonium phosphate, aluminum chloride,
Attaching about 5% by weight or more of ammonium bromide, zinc chloride, ammonium sulfate, ammonium sulfamate, guanidine sulfamate, guanidine phosphate, guanylurea phosphate, etc.
After that, it is preferable to oxidize by heating in an oxidizing atmosphere.

In the present invention, the limiting oxygen index (LOI) is J Is
It is a value measured according to the measurement method specified in -7201, and more specifically, it is as follows.

Wrap 1 g of the sample to be measured around a wire (support) with a diameter of about 1 mm, form a string with a diameter of about 4 mm, and fix it to a frame with a length of 15 Q mm. Next, this was set in a combustion cylinder, and after flowing a mixed gas of oxygen and nitrogen into it at a flow rate of 11.41/min for about 30 seconds, the upper end of the sample was ignited, and the sample was heated to 3.
The minimum oxygen flow rate (
Δ> and the nitrogen flow ff1(B) at that time are determined. The ratio of the oxygen flow m to the total flow rate of the mixed gas is the LOI, which is expressed by the following equation.

LOI=[A/(Δ+B)]X100 Below, the effects of the present invention will be specifically explained with reference to Examples.

Examples 1 to 5, Comparative Examples 1 to 4 AN97.5%, methyl acrylate 2.5% in DMSO
A with different intrinsic viscosities [η] shown in Table 1.
An N-based polymer was created. The polymer concentration of the obtained polymer solution was adjusted so that the solution viscosity was 3000 voices (45° C.) to prepare a spinning dope.

Using these spinning stock solutions, wet spinning and dry/wet spinning were performed, respectively. As a coagulation bath, a 55% DMSO aqueous solution at 20°C was used in all methods. Further, in the case of dry/wet spinning, the distance between the spinneret and the coagulating liquid level was set to 5 mm, and the distance from the coagulating liquid level to the focusing guide was 400 mm.

The obtained undrawn fiber yarn was drawn 5 times in hot water, and then
It was washed with water, applied with an oil agent, dried at 130'C, and densified. The dried and densified fibers were subjected to secondary drawing at a maximum drawing ratio of 90% in a dry heat tube at 180 to 200'C, and the single fiber fineness was approximately 2. Od, 1 g of acrylic fiber precursor having the fiber properties shown in Table 1.

2 each of the acrylic fiber precursors shown in Table 1
It was heated and oxidized under a relaxed state in air at 40'C. 1g
Table 2 shows the LOI of the flame-retardant acrylic fiber, the single fiber knot strength of the single fiber, and the spinnability of the acrylic flame-retardant fiber, which was crimped and cut into 102 mm pieces and tested using a model spinning machine. Indicated.

Example 6 The acrylic flame-resistant fiber of Comparative Example 3 having a single fiber knot strength of 2.6 CI and an IOI of 25 was immersed in an aqueous solution of guanidine phosphate and quickly dried to adhere 10% by weight of the guanidine phosphate. This flame-resistant acrylic fiber containing guanidine phosphate had an LOI of 47, a tensile strength of 3°4 c+/d, and a single fiber knot strength of 2.4 g, and exhibited excellent flame resistance and spinnability.

Claims (2)

[Claims] (1) Tensile strength of 1.5 to 4.5 g/d and at least 1
The limiting oxygen index (LOI) with a knot strength (monofilament) of g
) is 35 or more, an acrylic flame-resistant fiber with excellent abrasion resistance. (2) In claim 1, at least 10 acrylic flame-resistant fibers are obtained by dry/wet spinning.
An acrylic flame-resistant fiber with excellent abrasion resistance, which is an oxidized fiber whose precursor is an acrylonitrile fiber having a tensile strength of 2.2 g/d and a knot strength of 2.2 g/d or more.