KR930002075B1 - Process for production of aromatic polyamide pulp - Google Patents

Abstract

preparing the aromatic polyamide fiber or single fiber from the liquid crystal prepolymer of of the aromatic polyamide; precipitating the fiber or single fiber of the aromatic polyamide in sulfuric acid based water solution; and then pulverizing that. Pref. the time of pulverization is 10-10,000 sec, the sulfuric acid based water solution is selected from one or two of sulfuric acid, sulfuric acid chloride, or sulfuric acid fluoride of more 95 % concentration.

Description

Process for producing aromatic polyamide pulp

The present invention relates to a method for producing aromatic polyamide pulp, and more particularly, to a method for producing a new aromatic polyamide pulp having a very high specific surface area for lightening composite materials used in industrial applications.

In general, an aromatic polyamide fiber or its pulp is composed of a wholly aromatic polymer having an extended molecular chain, and has strong hydrogen bonds between these molecular chains, and thus has excellent physical properties as an organic synthetic fiber. In addition, the aromatic polyamide fibers have excellent heat resistance and very good chemical resistance properties, especially when the para-orientation has high strength and high elastic modulus as well as excellent chemical and mechanical stability. In particular, due to the high strength properties of aromatic polyamide fibers, research is ongoing to reduce the weight of composite materials in aerospace, leisure sports, and industrial hybrid applications.

Conventionally, various methods have been used to produce such aromatic polyamide pulp. For example, in US Pat. The resulting polymer was washed, separated and dried, and then dissolved in 98% or more concentrated sulfuric acid solvent to prepare a spinning dope, which was spun into water through detention to prepare fibers, which were cut and pulverized. Although a method for producing pulp has been proposed, in the case of producing pulp as described above, it is required to go through a complicated multi-step process, which leads to an increase in manufacturing cost, difficulty in continuous process, and as a dual structure of skin-core. When fibrils are formed only in the skin part during grinding, the specific surface area of the pulp There boundaries.

In US Pat. No. 4,511,623, the shear force is imparted in the polymerization accelerator precipitation solvent immediately before the completion of the aromatic polyamide polymerization. However, since this method imparts shear force in the solvent, the method is similar to the wet spinning method, but it is difficult to improve the physical properties in the process of manufacturing short fibers, but it is difficult to improve the physical properties, and the additional aging time after shear force is applied. This became necessary and difficult to manufacture continuously. And the molecular chain is a single structure arranged in a nematic (neutral end of the molecular chain with the ends of the molecular chain evenly distributed in one direction) in the fiber axis direction, but the molecular chain is tight to the inside of the fiber It is difficult to improve the specific surface area of the pulp by grinding.

Accordingly, an object of the present invention is to provide an aromatic polyamide pulp having a very high specific surface area and to reduce its weight by using a method for producing a new aromatic polyamide pulp in order to solve the above-mentioned problems.

Hereinafter, the present invention will be described in detail.

The present invention is applied to the surface of the fibers and short fibers produced by spinning or spraying the process through the spinneret in the state of the liquid crystal prepolymer before gelation in the process of polymerizing the aromatic polyamide, and the spinneret in the state of the prepolymer. The acid is treated to form cracks and then ground to produce pulp in a very bulky state. The reason for the acid treatment of such a surface is that the fiber and the single oil have a single structure in which molecular chains are formed nematically, and due to the strong hydrogen bonds between the molecular chains, it is difficult to produce pulp having excellent specific surface area. The specific surface area of the pulp thus prepared is increased by 20 to 100% compared to the conventional one.

Hereinafter, the present invention will be described in more detail.

In preparing the fibers and the short fibers in the present invention, as the polymerization solvent, Stir Opalesence during the polymerization reaction by adding an aromatic diamine and an aromatic dieside chloride to a solution in which an inorganic salt is dissolved in an amide solvent. Thereafter, the liquid crystal prepolymer formed at the point before gelation is spun through a detention or other short fiber manufacturing apparatus to produce aromatic polyamide fibers and short fibers. Amide solvents used herein include N-ethyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAC), and N, N-dimethylsulfoxide. Said (DMSO), N, N, N ', N'-tetramethylurea (TMU), hexamethylphosphoramide (HMPA), and 0.5 to 15% by weight of inorganic solvent based on the polymerization solvent to increase the solubility of the polymer. Salts are added, and inorganic salts include metal halides such as lithium chloride (LiC1), calcium chloride (CaC1), potassium chloride (KCl), potassium bromide (KBr) and lithium bromide (LiBr). In addition, the intrinsic degree of the liquid crystal prepolymer should have 1.0 dl / 9 to 4.0 dl / g, and more preferably 1.5 to 3.5 intrinsic viscosity in terms of process control. Because when the intrinsic viscosity is 1.0 or less, the molecular weight of the fiber does not increase, and the physical property is accompanied, and when it is 4.0 or more, process management is difficult.

The aromatic polyamide fibers and the short fibers used in the surface treatment of the present invention have a physical property of at least IV4.0dl / g and a strength of at least 15g / d, and the molecular structure inside is arranged in a nematic state with molecular chains in the fiber axis direction. It is a united structure. Molecular chains form strong hydrogen bonds and are made up to the inside of the fiber. Such aromatic polyamide fibers and short fibers are immersed in an aqueous solution using sulfuric acid, chlorosulfuric acid, fluorosulfuric acid alone or two or more kinds of mixed solvents. The immersion time is preferably 10 to 10,000 seconds. When it exceeds 10,000 seconds, the physical properties of the aromatic polyamide fibers are lowered, and when it is 10 seconds or more, the effect of the present invention does not appear. In addition, the sulfuric acid aqueous solution using a concentration of 95% sulfuric acid is preferably a ratio of sulfuric acid to water of 0.1 to 30. If the concentration of sulfuric acid is more than 30, the physical properties of the product are lowered. If the concentration is less than 0.1, the concentration of sulfuric acid is light, so that the present invention does not appear.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLES 1-4 COMPARATIVE EXAMPLES 1-2

In a solution of 100 cc of 95% sulfuric acid dissolved in 1000 cc of water, 100 g of aromatic polyamide fiber having IV5.1 dl / g of physical property was immersed, and after a predetermined time, the fibers were washed with water and crushed with a disk-type grinder. Physical properties of the obtained pulp are shown in Table 1. When the immersion time is 1 second, there is no effect of the present invention, and when the immersion time reaches 20,000 seconds, the physical properties decrease and become powder form.

TABLE 1

[Examples 5 to 6 Comparative Examples 3 to 4]

The physical properties of the pulp obtained by immersing the fibers after washing for 500 seconds by immersing the aromatic polyamide short fibers having the physical property of I.V.5.2dl / g in a solution of 100 cc of sulfuric acid having a concentration of 95% in water is shown in Table 2. At this time, the ratio of sulfuric acid and water was different. When the ratio of sulfuric acid to water is 30 or more, the physical properties of the pulp are lowered and the powder becomes powdery, so the effect of the present invention is lost.

TABLE 2

[Examples 8 to 13]

100 g of aromatic polyamide fiber having IV of 5.3 dl / g was immersed for 500 seconds in an aqueous solution of 1000-2000 cc of a mixed solvent of sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, etc. The physical properties of the pulp are shown in Table 3.

TABLE 3

Claims (4)

A method for producing an aromatic polyamide pulp, characterized in that the aromatic polyamide fibers and the short fibers prepared from the liquid crystal prepolymer of the aromatic polyamide are immersed in an aqueous sulfuric acid solution and then ground. The method of claim 1, wherein the immersion time is in the range of 10 seconds to 10,000 seconds. The method for producing an aromatic polyamide pulp according to claim 1, wherein the sulfuric acid aqueous solution is composed of sulfuric acid, chlorosulfuric acid, and fluorosulfuric acid having a concentration of 95% or more alone or two or more thereof. The method for producing an aromatic polyamide pulp according to claim 1, wherein the sulfuric acid aqueous solution has a ratio of sulfuric acid to water of 0.1 to 30.