JPH07197317A - Flame-retardant p-type aromatic polyamide fiber and its production - Google Patents

Abstract

PURPOSE:To obtain a p-type aromatic polyamide fiber useful for rope, tire, belt, etc., having excellent permanence and flame retardancy by adding a flame retardant to a p-type aromatic polyamide having a specific intrinsic viscosity. CONSTITUTION:This flame-retardant p-type aromatic polyamide fiber is obtained by adding a flame retardant to a p-type aromatic polyamide having <=2.5dl/g intrinsic viscosity. Since an aromatic diamine in an amount more than stoichiometry is reached, the end of molecular chain is substantially an amino group and the fiber has excellent grab of the flame-retardant and fastness to washing, wear, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant para-aromatic polyamide fiber (hereinafter, aromatic polyamide may be referred to as aramid) and a method for producing the same. Para-aramid fiber is used for ropes, tires, belts, bulletproof vests, etc. by utilizing its excellent mechanical properties such as high strength and high elastic modulus. Furthermore, by taking advantage of its excellent heat resistance and chemical resistance, it is also used in heat-resistant protective clothing and the like.

[0002]

2. Description of the Related Art Conventionally, para-aramid fiber has been used in various fields such as ropes, tires, belts and bulletproof vests by taking advantage of its features such as high specific strength, specific elastic modulus and excellent heat resistance. Further, as can be seen from the fact that the oxygen index (LOI value) of para-aramid fiber is 29, it is superior in flame retardancy to conventional fibers for clothing such as nylon and polyester. However, as the performance requirements in various fields such as flame-resistant curtains in hospitals and seat covers for airplanes become more severe, the emergence of para-aramid fibers with even higher flame retardancy is strongly demanded.

Various methods have conventionally been proposed for obtaining flame-retardant aromatic polyamide fibers.
For example, Japanese Examined Patent Publication (Kokoku) No. 55-51069 proposes a method of imparting flame retardancy by treating a meta-aramid fiber with an aromatic amine and then treating it with a halogen-substituted phosphazene or the like. However, in this method, since the flame retardant is not sufficiently fixed with para-aramid having higher crystallinity than meta-aramid, it is not possible to obtain a durable flame-retardant para-aramid fiber. Then, JP-A 1-2221537
As disclosed in Japanese Unexamined Patent Application Publication No. JP-A No. 2003-242242, a method in which meta-aramid fiber and para-aramid fiber are mixed-spun, or a method of using a woven fabric of flame-retardant wool fiber and para-aramid fiber in a two-layer structure, as disclosed in JP-A-3-837, is used. Attempts have been made, but sufficient performance has not yet been obtained.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a para-aramid fiber having durability and excellent flame retardancy, and a production method for obtaining the same.

[0005]

That is, the present invention for solving the above problems comprises the following inventions. (1) A flame-retardant para-aromatic polyamide fiber comprising a flame-retardant and comprising para-aromatic polyamide having an intrinsic viscosity of 2.5 dl / g or less. (2) The flame-retardant para-aromatic polyamide fiber according to item (1), wherein the terminal of the para-aromatic polyamide molecule is substantially an amino group. (3) A polar amide solution containing 4 to 10% by weight of a para-aromatic polyamide having an intrinsic viscosity of 2.5 dl / g or less and 2 to 10% by weight of a chloride of an alkali metal or an alkaline earth metal. A step of obtaining a combined dope, a step of spinning a para-aromatic polyamide from the polymer dope and coagulating it in an aqueous coagulating liquid, and a solution or dispersion of an aqueous flame retardant in a state where the obtained fiber is swollen with water. A method for producing a flame-retardant para-aromatic polyamide fiber, which comprises a step of contacting and a step of drying. (4) The polymer dope has a para-aromatic polyamide concentration of 4 to 10 wt% in a polar amide solvent in which 2 to 10 wt% of an alkali metal or alkaline earth metal chloride is dissolved. The para-oriented aromatic diamine halide is added to 1.00 mol of the para-oriented aromatic diamine in an amount of 0.9.
The method for producing a flame-retardant para-aromatic polyamide fiber according to the above item (3), which is obtained by adding 4 to 0.99 mol and polymerizing at a temperature of -20 to 50 ° C. (5) The method for producing a flame-retardant para-aromatic polyamide fiber according to the above item (3) or (4), characterized in that each step is continuously carried out.

The present invention will be described in detail below. In the present invention, a para-aromatic polyamide (para-aramid)
Is obtained by polycondensation of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an orientation position corresponding thereto (eg, 4,4′-biphenylene). , 1,5-naphthalene, 2,6-naphthalene, etc., consisting essentially of repeating units bound in opposite or coaxially extending directions), such as poly (paraphenylene terephthalamide). , Poly (4,4'-benzanilide terephthalamide), poly (paraphenylene-4,4'-
Specific examples thereof include aromatic polyamides having a para-orientation type or a structure close to the para-orientation type, such as biphenylene dicarboxylic acid amide) and poly (paraphenylene-2,6-naphthalene dicarboxylic acid amide).

In the present invention, the intrinsic viscosity of the para aromatic polyamide is 2.5 dl / g or less. By selecting this intrinsic viscosity range, as will be described later, the polymerization liquid can be directly spun as a spinning dope, and it is not necessary to use highly corrosive concentrated sulfuric acid as a spinning solvent as in the case of a polymer having a higher intrinsic viscosity. The process is simplified and it is excellent in economic efficiency. In addition, as a result of using an aromatic diamine in excess of the stoichiometry in order to make the intrinsic viscosity 2.5 dl / g or less, it is suggested that the molecular chain end is substantially an amino group. Therefore, in the case of a flame retardant having affinity or reactivity with an amino group, an effect of fixing the flame retardant in the fiber is also expected. By treating such a para-aromatic polyamide fiber with a water-based flame retardant in a state swollen with water, it is possible to obtain a para-aramid fiber having particularly excellent flame retardancy.

In the present invention, the state in which para-aramid is swollen with water specifically means, for example, the state in which para-aramid is coagulated in an aqueous coagulating liquid by spinning or the like,
Apparently, it means that water is present in the para-aramid fiber. In particular, the water-swollen para-aramid fiber of the present invention has a high water content of 70 to 85% by weight, and is considered to be able to rapidly absorb the flame retardant. In the case of a para-aramid dope using concentrated sulfuric acid as a solvent, the dope becomes an isotropic solution when the para-aramid concentration is about 10% by weight or less. Spinning from an isotropic solution does not provide the high rigidity, high strength fibers characteristic of para-aramid. The dope of the present invention becomes a solution exhibiting optical anisotropy when the concentration of para-aramid is 4 to 10% by weight. As a result, a wet fiber having the characteristics of crystalline fiber and having a high water content in a wet state was obtained.

The para-aramid fiber of the present invention is produced by spinning from a polymer dope (spinning dope) containing para-aramid having an intrinsic viscosity of 2.5 dl / g or less. Specifically, a polymer dope, which is a polar amide solution containing 4 to 10% by weight of para-aramid and 2 to 10% by weight of a chloride of an alkali metal or an alkaline earth metal, is used as it is as a spinning dope, and a wet or dry wet ( Para-aramid fiber is produced by spinning according to the method (sometimes referred to as air gap spinning). The spinning dope of the composition shows a liquid crystal state, and high strength and high rigidity para-aramid fiber can be obtained.

At this time, the para-aramid dope, which has a low degree of polymerization and is considered to have the terminal of the para-aramid molecule substantially as an amino group, has dissolved, for example, 2 to 10% by weight of an alkali metal or alkaline earth metal chloride. In a polar amide-based solvent, a para-oriented aromatic diamine halide was added in an amount of 0.94 to 0.99 to 1.00 mol of the para-oriented aromatic diamine so that the para-aramid concentration was 4 to 10% by weight.
It is produced by adding mols, preferably 0.95 to 0.98 mol, and polymerizing at a temperature of -20 to 50 ° C.

The shape of the para-aramid fiber when subjected to the flame-retardant treatment in a state swollen with water can be selected from long fiber, staple, chopped fiber, pulp and the like depending on the application. In the present invention, almost any flame retardant that can be dissolved or dispersed in water can be used. For example, antimony oxide, high bromine compound flame retardant, phosphorus compound flame retardant, high chlorine compound flame retardant and the like. It is possible to obtain the desired flame-retardant para-aramid fiber by subjecting para-aramid fiber having an intrinsic viscosity of 2.5 dl / g or less swollen with water using these flame retardants to a flame-retardant treatment by a conventional method. it can. The flame retarding treatment is generally performed by immersing the fiber in a treatment bath in which a flame retardant is dissolved or dispersed in water. As the condition of the flame retardant treatment, the condition generally recommended for the flame retardant depending on the type of the flame retardant used can be used as it is. At this time, the pH of the treatment bath is preferably in the range of 5 or more and 9 or less in order to minimize the decrease in fiber strength. At the same time, chemicals such as dyes, pastes, antioxidants, light resistance imparting agents and softening agents can be added to further enhance the functionality. After the treatment with the flame retardant, it is washed with water to wash off excess treatment agent adhering to the fiber surface, and then dried to obtain the target flame-retardant para-aramid fiber.

According to the present invention, the intrinsic viscosity of para-aramid is 2.5 dl / g, which is a relatively small molecular weight, and the end of the molecule is a polymer having a substantially amino group as a raw material. Fiber strength is 5-16g / d
Although it is lower than ordinary para-aramid fiber, it is not inferior to other industrial and clothing fibers such as nylon, and physicochemical performance such as heat resistance and chemical resistance is usually It is almost the same as the para-aramid fiber. Furthermore, since fibers made from a polymer having a relatively small molecular weight in a state swollen with water are treated, the treatment agent is evenly dispersed and firmly held inside the fibers, so that against washing and abrasion. Durable flame-retardant para-aramid fibers are obtained. The method of the present invention is an industrially advantageous method for producing a flame-retardant para-aramid fiber because each step from polymerization to flame-retardant treatment can be continuously carried out.

[0013]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The tests, evaluation methods and criteria in Examples and Comparative Examples are as follows. 1. Method for measuring intrinsic viscosity The flow time was measured at 30 ° C. with a capillary viscometer for a solution in which 0.5 g of para-aramid was dissolved in 100 ml of 96-98% sulfuric acid and 96-98% sulfuric acid itself. Intrinsic viscosity was calculated from the calculated flow rate ratio by the following formula. Intrinsic viscosity = ln (T / T ₀ ) / C [unit: dl / g] where T and T ₀ are the flow times of the para-aramid sulfuric acid solution and sulfuric acid, respectively, and C is the concentration of the para-aramid solution (g / dl). Represents

2. Single Fiber Strength JIS L 1015 "Chemical Fiber Staple Test Method"
The measurement was carried out under the following conditions according to the method described in 1. (1) Fineness: Vibroscope method (2) Strength: Gauge length 10 mm, crosshead speed 1
mm / min 3. Flame retardancy Flame retardancy was determined by putting fibers in a flame, igniting them, and observing the state of continuous combustion.

Synthesis Example 1 (Preparation of short para-aramid fiber) A short fiber of polypara (phenylene terephthalamide) swollen with water was obtained by the method described below. 1. Polymerization Stirrer, thermometer, nitrogen inflow pipe and powder addition port 5
Polymerization of para (phenylene terephthalamide) was carried out using a 00 ml separable flask. After the flask was sufficiently dried, 0.135 mol of dried calcium chloride was added to 300 g of NMP and completely dissolved at an internal temperature of 85 ° C. Next, 0.120 mol of paraphenylenediamine (hereinafter sometimes abbreviated as PPD) was added and dissolved, and after cooling until the internal temperature reached -6 ° C, the internal temperature was kept at 5 ° C or lower to give a value of 0. 115 mol of terephthaloyl chloride (hereinafter sometimes abbreviated as TPC) was gradually added. After the addition of TPC was completed, the mixture was aged at a temperature of -6 to 0 ° C for 2 hours to obtain a stable liquid polymer dope. The intrinsic viscosity of this polypara (phenylene terephthalamide) was measured and found to be 1.8 dl / g.

2. Spinning The polymer dope of para-aramid thus obtained was spun using an aqueous solution containing 20 wt% of NMP as a coagulating liquid. As the spinning nozzle, a hole having a cone shape and a tip end having a cylindrical shape, the cylindrical hole portion having an L / D of 1, and having a hole diameter of 0.07 mm was used. After spinning, the fiber was thoroughly washed with water and cut into fiber lengths of about 60 mm to obtain para-aramid short fibers swollen with water. A part of this short fiber was collected and dried at 120 ° C for 2 hours, and the solid content was about 2
It was 0% by weight. The single fiber strength of this fiber was 8 g / d.

Example 1 The water-swollen short para-aramid fibers obtained in Synthesis Example 1 were collected in a dry weight of 5 g in a 300 ml eggplant-shaped flask. Then, bromine, phosphorus compound type flame retardant,
Product name: Polysafe WA-06 (manufactured by Ajinomoto Co., Inc.) 25
% Aqueous solution was added. After setting the reflux condenser, it was refluxed in an oil bath for 4 hours for flame-retardant treatment. After cooling, it was taken out, washed with water and dried at 95 ° C. to obtain a flame-retardant para-aramid fiber. It was found that the obtained flame-retardant para-aramid fiber was placed in a flame for 4 to 5 seconds but did not ignite, and showed excellent flame retardancy.

Comparative Example 1 5 g of the wet para-aramid fiber obtained in Synthesis Example 1 was taken as a dry weight thereof, dried in an oven at 150 ° C. for 2 hours, and then flame retarded in the same manner as in Example 1. Processed. The flame retardancy of the obtained para-aramid fiber was evaluated in Example 1
However, the flame was extinguished in the flame, and the flame was extinguished after 1 to 2 seconds. Although this flame retardancy was superior to that of ordinary clothing fibers, it was extremely inferior to that of Example 1.

Comparative Example 2 The wet para-aramid fiber obtained in Synthesis Example 1 was dried in an oven at 150 ° C. for 2 hours, and the flame retardancy of the fiber was examined in the same manner as in Example 1. Similar to Example 1, it was very inferior to that of Example 1.

Comparative Example 3 Commercially available para-aramid staple (single fiber strength 18 g /
d, the intrinsic viscosity of the raw material para-aramid is estimated to be 3.5 or more. The flame retardancy of 1) was examined in exactly the same manner as in Example 1, but was very inferior to that in Example 1 as in Comparative Example 1.

The para-aramid fiber thus obtained has good durability and particularly excellent flame retardancy, so that it can be used in a flameproof curtain of a hospital or a seat cover of an aircraft.
It can be suitably used for applications requiring heat resistance and flame resistance.

[0022]

EFFECTS OF THE INVENTION According to the method of the present invention, the flame retardant is evenly dispersed and firmly held inside the fiber. Therefore, in addition to the heat resistance of the para-aramid fiber, it has durability against washing and abrasion. It is possible to obtain excellent flame-retardant para-aramid fiber. Further, since each step from polymerization to flame retardation treatment can be continuously carried out, it is an industrially advantageous method for producing a flame-retardant para-aramid fiber.

Claims (5)

[Claims] 1. A flame retardant is contained, and the intrinsic viscosity is 2.5 dl /
A flame-retardant para-aromatic polyamide fiber comprising a para-aromatic polyamide having a weight of g or less. 2. The flame-retardant para-aromatic polyamide fiber according to claim 1, wherein the terminal of the molecule of the para-aromatic polyamide is substantially an amino group. 3. A polar amide solution containing 4 to 10% by weight of a para-aromatic polyamide having an intrinsic viscosity of 2.5 dl / g or less and 2 to 10% by weight of an alkali metal or alkaline earth metal chloride. A step of obtaining a polymer dope, a step of spinning a para aromatic polyamide from the polymer dope and coagulating it in an aqueous coagulating liquid, a solution or dispersion of an aqueous flame retardant in a state where the obtained fiber is swollen with water A method for producing a flame-retardant para-aromatic polyamide fiber, which comprises a step of contacting with a liquid and a step of drying. 4. The polymer dope has a para-aromatic polyamide concentration of 4 to 1 in a polar amide solvent in which 2 to 10% by weight of an alkali metal or alkaline earth metal chloride is dissolved.
1.0% of para-oriented aromatic diamine so as to be 0% by weight
0.94 to 0.99 mol of para-oriented aromatic dicarboxylic acid halide is added to 0 mol, and the temperature is -20 to 50 ° C.
The method for producing a flame-retardant para-aromatic polyamide fiber according to claim 3, which is obtained by polymerizing with. 5. The method for producing a flame-retardant para-aromatic polyamide fiber according to claim 3, wherein each step is continuously carried out.