JP2011236511A - Para-type wholly aromatic polyamide fiber and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a para-type wholly aromatic polyamide fiber having mechanical strength and high shrinkability under high temperature conditions, and a method for manufacturing the fiber.SOLUTION: A method for manufacturing a para-type wholly aromatic polyamide fiber comprises a step of hot drawing and a subsequent step of heat treatment under a low oxygen atmosphere in a specified range of temperature. More particularly, after the hot drawing step, the heat treatment is performed under an atmosphere having an oxygen concentration of 1 vol.% or less at a temperature of 450 to 550°C.

Description

  The present invention relates to a para-type wholly aromatic polyamide fiber and a method for producing the fiber. More specifically, the present invention relates to a para-type wholly aromatic polyamide fiber having mechanical strength and high shrinkage under high temperature conditions, and a method for producing the fiber.

  A wholly aromatic polyamide produced from an aromatic diamine and an aromatic dicarboxylic acid dihalide is excellent in heat resistance and flame retardancy. For this reason, wholly aromatic polyamid fibers are useful as heat-resistant and flame-retardant fibers, and are used in fields that exhibit these characteristics, such as industrial applications such as filters and electronic parts, heat resistance, flame resistance, and flame resistance. Is used in disaster prevention safety clothing applications such as protective clothing.

Among them, protective clothing includes protective clothing worn in front of high-temperature furnaces such as blast furnaces, electric furnaces and incinerators, fire-resistant clothing for people engaged in fire fighting work, welding protective clothing for welding work exposed to high-temperature sparks, and ignition. Widely used as flame retardant work clothes for people who handle highly chemicals.
However, there is no need for fire resistance, flame resistance, and heat resistance in protective clothing, as there is no need for early entry into the flame scene, further access to the fire source, and further safety improvements for firefighters, etc. A level was sought.

Therefore, in recent years, for the purpose of improving the fire protection performance of the protective clothing, a laminated protective clothing having an improved heat shielding property by providing an air layer inside the laminated structure has been proposed (Patent Document 1). And 2).
In Patent Documents 1 and 2, by using different materials having different heat shrinkability as different layers, a difference in heat shrinkability at the time of exposure to a flame is utilized to generate voids in the laminated structure.

Here, with respect to meta-type wholly aromatic polyamide fibers, there has been proposed a technique for increasing the shrinkage rate of fibers while maintaining strength by controlling the crystal structure of the fibers (see Patent Document 3). However, since the meta-type wholly aromatic polyamide fiber is originally not sufficiently high in mechanical strength, when used as a protective garment, it is necessary to increase the total basis weight in order to ensure the fabric strength. There was a problem that the weight of the protective clothing obtained increased.
Therefore, a para type wholly aromatic polyamide fiber having mechanical strength and the like and a fiber having a high shrinkage rate has been expected.

JP-T-2006-516306 JP-T-2005-507468 JP-A 63-235523

  The present invention has been made against the background of the above-described conventional technology. The object of the present invention is to provide a para-type wholly aromatic polyamide fiber having mechanical strength and high shrinkage under high temperature conditions, and It is in providing the manufacturing method of a fiber.

  The present inventor has intensively studied to solve the above problems. As a result, in the production of para-type wholly aromatic polyamide fiber, it has been found that the above-mentioned problems can be solved by heat treatment in a specific temperature range under a low oxygen atmosphere after passing through a heat stretching step, and the present invention has been completed. .

That is, the present invention is a para-type wholly aromatic polyamide fiber having a dry heat shrinkage of 500 ° C. of 10% or more and a tensile strength of 18 cN / dtex or more.
Another aspect of the present invention is a method for producing a para-type wholly aromatic polyamide fiber having the above physical properties, and after passing through a heat stretching step, in an atmosphere having an oxygen concentration of 1% by volume or less, at a temperature of 450 to 550 ° C. A method for producing para-type wholly aromatic polyamide, characterized by heat treatment.

  The para-type wholly aromatic polyamide fiber of the present invention has high shrinkage under high temperature conditions while having mechanical strength. Therefore, the fiber of the present invention is extremely useful as a fiber material for protective clothing having excellent heat shielding properties, and is extremely effective not only for the flame resistance of protective clothing but also for weight reduction.

Hereinafter, embodiments of the present invention will be described in detail.
<Para-type wholly aromatic polyamide>
The para-type wholly aromatic polyamide in the present invention is a polymer in which one or more divalent aromatic groups are directly linked by an amide bond. Aromatic groups include those in which two aromatic rings are bonded via an oxygen, sulfur or alkylene group, or those in which two or more aromatic rings are directly bonded. Furthermore, these divalent aromatic groups may contain a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a methoxy group, a chloro group, or the like. Note that the position of the amide bond directly linking the divalent aromatic group is a para type.

<Method for producing para-type wholly aromatic polyamide>
The para-type wholly aromatic polyamide in the present invention can be produced according to a conventionally known method. For example, a polymer solution of an aromatic polyamide can be obtained by reacting an aromatic dicarboxylic acid chloride component and an aromatic diamine component in an amide polar solvent.

[Para-type wholly aromatic polyamide raw material]
(Aromatic dicarboxylic acid dichloride component)
The aromatic dicarboxylic acid chloride component used as a raw material for the para-type wholly aromatic polyamide used in the present invention is not particularly limited, and generally known compounds can be used. Examples thereof include terephthalic acid chloride, 2-chloroterephthalic acid chloride, 2,5-dichloroterephthalic acid chloride, 2,6-dichloroterephthalic acid chloride, 2,6-naphthalenedicarboxylic acid chloride and the like. These aromatic dicarboxylic acid dichlorides can be used not only in one type but also in two or more types, and the composition ratio is not particularly limited. Of these, terephthalic acid dichloride is preferred from the viewpoints of versatility and mechanical properties of the resulting fiber.

(Aromatic diamine component)
The aromatic diamine component used as a raw material for the para-type wholly aromatic polyamide used in the present invention is not particularly limited, and generally known ones can be used. For example, p-phenylenediamine, 2-chloro-p-phenylenediamine, 2,5-dichloro-p-phenylenediamine, 2,6-dichloro-p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4 ' -Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone and the like can be mentioned. These can use not only one type but also two or more types, and the composition ratio is not particularly limited.

  Among these, from the viewpoint of mechanical strength of the resulting fiber, it is preferable to use p-phenylenediamine and 3,4'-diaminodiphenyl ether alone or in combination, and p-phenylenediamine and 3,4 A combination with '-diaminodiphenyl ether is most preferred. When paraphenylenediamine and 3,4'-diaminodiphenyl ether are used in combination, the composition ratio is not particularly limited, but is 30 to 70 mol% and 70, respectively, based on the total aromatic diamine amount. It is preferable to set it as -30 mol%, More preferably, it is 40-60 mol%, 60-40 mol%, respectively, Most preferably, it is respectively 45-55 mol%, 55-45 mol%.

(Combination of aromatic dicarboxylic acid dichloride component and aromatic diamine component)
Accordingly, examples of the para-type wholly aromatic polyamide used in the present invention include copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, polyparaphenylene terephthalamide, and the like.

[Raw material composition ratio]
The ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component as a raw material for the aromatic polyamide is in the range of 0.90 to 1.10 as the molar ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component. It is preferable that the range is 0.95 to 1.05. When the molar ratio of the aromatic dicarboxylic acid chloride component is less than 0.90 or exceeds 1.10, the reaction with the aromatic diamine component does not proceed sufficiently and a high degree of polymerization cannot be obtained, which is not preferable.

[Reaction conditions]
The reaction conditions for the aromatic dicarboxylic acid chloride component and the aromatic diamine component are not particularly limited. The reaction between acid chloride and diamine is generally rapid, and the reaction temperature is preferably, for example, in the range of -25 ° C to 100 ° C, more preferably in the range of -10 ° C to 80 ° C.

[Polymerization solvent]
Examples of the solvent used for the polymerization of the para-type wholly aromatic polyamide used in the present invention include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP). Organic polar amide solvents such as N-methylcaprolactam, water-soluble ether compounds such as tetrahydrofuran and dioxane, water-soluble alcohol compounds such as methanol, ethanol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, Water-soluble nitrile compounds such as acetonitrile and propionitrile are listed. These solvents can be used singly or as a mixed solvent of two or more. Note that the solvent used is preferably dehydrated.

  In the production of the para-type wholly aromatic polyamide used in the present invention, N-methyl-2-pyrrolidone (NMP) is used from the viewpoints of versatility, harmfulness, handleability, solubility in para-type wholly aromatic polyamide, and the like. Most preferably, it is used.

[Other polymerization conditions]
In order to increase the solubility of the resulting para-type wholly aromatic polyamide, an appropriate amount of a generally known inorganic salt may be added either before, during or at the end of polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.
Moreover, the terminal of para-type wholly aromatic polyamide can also be sealed. When the terminal is sealed with a terminal blocking agent, for example, phthalic acid chloride and its substituted product, aniline and its substituted product, and the like can be used as the terminal blocking agent.

In addition, aliphatic or aromatic amines, quaternary ammonium salts, and the like can be used in combination in order to capture an acid such as hydrogen chloride.
After completion of the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like may be added as necessary to carry out a neutralization reaction.

[Post-polymerization, etc.]
The para-type wholly aromatic polyamide obtained as described above can be put into a non-solvent such as alcohol or water, precipitated, and then taken out as a pulp. The para-type wholly aromatic polyamide taken out can be dissolved again in another solvent and then used for fiber molding, but the polymer solution obtained by the polymerization reaction is directly used as a spinning solution (dope). It is also possible. The solvent used for taking out once and dissolving it again is not particularly limited as long as it dissolves the para-type wholly aromatic polyamide, and the solvent used for the polymerization of the para-type wholly aromatic polyamide and It is preferable to do.

<Method for producing para-type wholly aromatic polyamide fiber>
In the method for producing a para-type wholly aromatic polyamide fiber of the present invention, a wet spinning method or a semi-dry semi-wet spinning method is adopted. That is, first, a spinning solution (polymer dope) containing para-type wholly aromatic polyamide and a solvent is discharged from a spinneret to form a coagulated yarn. Then, after removing the solvent contained in the coagulated yarn, hot drawing is performed, and subsequently, heat treatment is performed in a specific temperature range under a low oxygen atmosphere to obtain a final para-type wholly aromatic polyamide fiber.

Hereinafter, the method for producing a para-type wholly aromatic polyamide will be described separately for each step.
[Process for adjusting spinning solution (polymer dope)]
In obtaining the para type wholly aromatic polyamide fiber, first, in the spinning solution (polymer dope) adjusting step, a spinning solution (polymer dope) containing the para type wholly aromatic polyamide and the solvent is adjusted.

  The method for adjusting the spinning solution (dope) containing the para-type wholly aromatic polyamide and the solvent is not particularly limited. Moreover, it is preferable to use the solvent used for superposition | polymerization of the above para type wholly aromatic polyamide as a solvent used for preparation of the solution for dope (dope). In addition, the solvent used may be one type alone or a mixed solvent obtained by mixing two or more types of solvents. In the production method of the present invention, the polymer can be used as it is without being isolated from the polymer solution obtained by the production of the para-type wholly aromatic polyamide.

  Moreover, you may mix | blend other arbitrary components, such as an additive, in the range which does not exceed the summary of this invention in order to provide functionality etc. to a fiber. When an additive or the like is blended, it can be introduced in adjusting the dope. The method of introduction is not particularly limited, and for example, it can be introduced into the dope using a ruder or a mixer.

  The polymer concentration in the spinning solution (dope), that is, the concentration of the para-type wholly aromatic polyamide is preferably in the range of 0.5 to 30% by mass, more preferably in the range of 1 to 20% by mass. preferable. When the polymer concentration in the spinning solution (dope) is less than 0.5% by mass, the entanglement of the polymer is small, so that the viscosity necessary for spinning cannot be obtained, and the ejection stability during spinning decreases. . On the other hand, when the polymer concentration exceeds 30% by mass, the viscosity of the dope increases abruptly, so that the discharge stability at the time of spinning decreases, and stable spinning is performed by the rapid pressure increase in the spinning pack. It becomes difficult.

[Spinning and coagulation process]
Next, in the spinning / coagulation step, the spinning solution (polymer dope) obtained above is discharged from the spinneret and solidified by passing through the coagulating liquid to obtain a coagulated yarn.
In spinning, the spinning solution (polymer dope) may be discharged directly into the coagulation bath, or an air gap made of air or inert gas is provided and discharged into the coagulation bath through the air gap. Also good.

Generally, a poor solvent for aromatic polyamide is used as the coagulating liquid filled in the coagulating bath. At this time, it is usual to adjust the coagulation rate by adding a good solvent so that the solvent escapes from the aromatic polyamide dope so rapidly that the formed coagulated yarn is not defective. In general, it is preferable to use water as the poor solvent and a solvent for the aromatic polyamide dope as the good solvent. The composition ratio of good solvent / poor solvent may be appropriately selected depending on the solubility and coagulation property of the aromatic polyamide to be used, but is generally preferably in the range of 15/85 to 40/60.
The temperature of the coagulation liquid is not particularly limited, and can be set as appropriate depending on the composition of the coagulation liquid and the solubility and coagulability of the aromatic polyamide used.

[Stretching process]
Further, in the production of para-type wholly aromatic polyamide fibers, it is common to give orientation to the fibers by drawing for the purpose of improving the mechanical strength. The place of drawing is not particularly limited. Immediately after the spinning / coagulation step, washing drawing in a coagulated yarn state, boiling water drawing, and the like may be performed.

[Hot drawing process]
In the present invention, in the hot drawing step, the unstretched coagulated yarn or the coagulated yarn that has been stretched is dried in the dry yarn state after the coagulated yarn is dried to obtain a dry yarn. is required.

At the stage of the unstretched coagulated yarn or the stretched coagulated yarn, the fibers are not yet fully oriented. For this reason, in the present invention, after the coagulated yarn is dried to form a dried yarn, hot drawing is performed. By this hot drawing, the para-type aromatic polyamide forming the fiber is highly oriented and crystallized, so that the fiber has sufficient mechanical strength.
The temperature of the hot stretching is preferably 300 ° C. or more and 550 ° C. or less although it depends on the polymer skeleton of the para type wholly aromatic polyamide. Moreover, it is preferable that a draw ratio shall be 10 times or more.

[Low oxygen heat treatment process]
The fiber that has undergone the above-described hot drawing process has been highly oriented and crystallized, and has already sufficiently developed its mechanical strength. However, the high shrinkage property under the high temperature condition which is the subject of the present invention cannot be obtained. Therefore, in the present invention, it is necessary to perform heat treatment in a specific temperature range in a low oxygen atmosphere in a low oxygen heat treatment step on the fiber after undergoing the heat drawing step.
The oxygen concentration in the low oxygen heat treatment step is 1% by volume or less. Preferably it is 0.5 volume% or less. When the oxygen concentration exceeds 1% by volume, decomposition of the polymer chain is promoted by the oxygen present, and sufficient tensile strength cannot be obtained.

The heat treatment temperature needs to be in the range of 450 to 550 ° C. When the heat treatment temperature is lower than 450 ° C., the orientation of the amorphous part of the fiber cannot be changed, and it becomes difficult to exhibit high shrinkage. On the other hand, if the temperature exceeds 550 ° C., the fiber causes thermal deterioration, so that sufficient tensile strength cannot be obtained.
The heat treatment time is desirably 1 minute or less. When the heat treatment time exceeds 1 minute, decomposition of the polymer chain is promoted, and sufficient tensile strength cannot be obtained.

<Physical properties of para-type wholly aromatic polyamide fiber>
The para type wholly aromatic polyamide fiber obtained by the production method of the present invention has a dry heat shrinkage of 500 ° C. of 10% or more and a tensile strength of 18 cN / dtex or more.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these description.

<Measurement and evaluation method>
Each characteristic value in Examples and Comparative Examples was measured and evaluated by the following method.

(1) Fineness Measured according to JIS-L-1015 B method.

(2) Tensile strength Using a tensile tester (Orientec Co., Ltd., trade name: Tensilon universal tester, model: RTC-1210A), measurement was performed under the following conditions based on the procedure of ASTM D885.
[Measurement condition]
Measurement sample length: 500 mm
Initial load: 0.2 cN / dtex
Tensile speed: 250 mm / min

(3) 500 degreeC dry heat shrinkage rate When the initial length of a fiber is set to Lo and the fiber length after performing the drying heat treatment of 500 degreeC atmosphere with respect to the said fiber for 10 minutes is set to L, it calculates with a following formula ( S) was defined as the dry heat shrinkage.
[Formula 1]
S (%) = (Lo−L) / Lo × 100

<Example 1>
Concentration of copolyparaphenylene 3,4'-oxydiphenylene terephthalamide (inherent viscosity (IV) = 3.4 measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dL in 98% concentrated sulfuric acid) A 6% by mass NMP solution was prepared as a spinning solution.
The obtained spinning solution was discharged from a spinneret with 25 holes, and spun into an aqueous solution with an NMP concentration of 30% by mass through an air gap of about 10 mm (semi-dry semi-wet spinning method). , Washed with water, dried, and hot stretched 10 times at a temperature of 530 ° C.
Subsequently, the heat-stretched fiber was heat-treated for 30 seconds in an atmosphere having an oxygen concentration of 0.2% by volume at a temperature of 500 ° C. The fiber after the heat treatment was wound up to obtain a para-type wholly aromatic polyamide fiber of 42 dtex / 25 fil.
Table 1 shows the physical properties and the like of the obtained fiber.

<Examples 2-5, Comparative Examples 1-5>
A para type wholly aromatic polyamide fiber was obtained in the same manner as in Example 1 except that the heat treatment conditions were changed as shown in Table 1. The physical properties and the like of the obtained fibers are summarized in Table 1.

  The para-type wholly aromatic polyamide fiber obtained by the production method of the present invention has high shrinkage under high temperature conditions while having mechanical strength. For this reason, in addition to fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics, fiber structures such as braids, ropes, twisted cords, yarns, and cotton can be configured, and in particular, high shrinkage under high temperature conditions is required. It can be suitably used as a fabric constituting a protective garment.

Claims (3)

  A para-type wholly aromatic polyamide fiber having a dry heat shrinkage of 500 ° C. of 10% or more and a tensile strength of 18 cN / dtex or more.   The para-type wholly aromatic polyamide fiber according to claim 1, wherein the para-type wholly aromatic polyamide fiber is copolyparaphenylene-3, 4 'oxydiphenylene terephthalamide fiber. A method for producing a para-type wholly aromatic polyamide fiber according to claim 1 or 2,
A method for producing a para-type wholly aromatic polyamide fiber, which is subjected to heat treatment at a temperature of 450 to 550 ° C in an atmosphere having an oxygen concentration of 1% by volume or less after undergoing a heat stretching step.