JP2006176950A - Polyparaphenylene terephthalamide (ppta) staple fiber and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polyparaphenylene terephthalamide (PPTA) staple fibers which hold the original high heat resistance and high Young's modulus thereof, have a small ion content, and are especially useful for electric/electronic parts, and to provide uses thereof. <P>SOLUTION: The polyparaphenylene terephthalamide (PPTA) staple fibers having a Na+ ion content of ≤1.0 wt.% and obtained by subjecting fibers having a crystal size (110 face) of ≤50Å, a diameter of 1 to 20 μm, and an aspect ratio of 50 to 5,000 to an extraction treatment using 20°C water. The staple fibers can be used for insulating/low dielectric materials, resin composite materials, rubber-composite materials or sheet-like structures for printed circuit boards. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyparaphenylene terephthalamide short fiber having a small ion content, a high Young's modulus, good dimensional stability, and excellent heat resistance and insulation, a method for producing the same, and a use thereof.

  Conventionally, polyparaphenylene terephthalamide (hereinafter abbreviated as PPTA) short fibers have been used as industrial and special clothing short fibers because they have excellent strength, heat resistance and high Young's modulus.

  PPTA fibers are formed into yarns having a high degree of crystallinity by applying concentrated sulfuric acid as a solvent for polymer dissolution during spinning to form a liquid crystal state, and then applying shear by a die. It is known that concentrated sulfuric acid as a solvent is washed with water and neutralized with alkali immediately after spinning, dried and heat-treated at 200 ° C. or higher, and then wound up as a filament (US Pat. No. 3,767,756). ).

  PPTA short fibers can be obtained by processing the fibers thus obtained so as to be fibrillated by cutting with a cutter or the like so as to have an aspect ratio of 50 to 5000 or by applying mechanical shear.

  However, in the short fibers obtained in this way, the salt formed by neutralization is incorporated into the fibers, and usually becomes short fibers containing 0.5 to 3% by weight of salt. For example, when sodium hydroxide is used during neutralization, the ions constituting the salt are mainly Na + and SO42−, and the molar ratio is about 2: 1.

  When short fibers are used under humid conditions, this salt may be ionized in the presence of water, and may hinder energization, such as when electrical insulation is required.

  On the other hand, paper, resin composites, rubber composites or fabrics made from PPTA short fibers have good dimensional stability and workability as insulating / low dielectric materials when used as electronic / insulating materials due to their polymer structure. It is known to exhibit excellent characteristics such as high Young's modulus and low shrinkage due to high temperature treatment. However, when energization due to such factors becomes a problem, for example, when it is used as a material for a printed wiring board, it may become a factor of migration via ions, which may limit application development. It was.

  The object of the present invention is to eliminate the drawbacks of the prior art described above, and to maintain a high heat resistance and a high Young's modulus inherent in PPTA short fibers, while having a small ion content, and particularly useful fibers and applications thereof as electrical / electronic parts. It is to provide.

  In order to solve the above problems, the present invention takes the following means.

(1) A polyparaphenylene having a crystal size (110 plane) of 50 angstroms or less, an alkali ion content of 1.0% by weight or less, a diameter of 1 to 20 μm, and an aspect ratio of 50 to 5000 Terephthalamide short fiber.

(2) Polyparaphenylene having a crystal size (110 plane) of 50 angstroms or less, an alkali ion content of 1.0% by weight or less, and fibrillated with a length of 0.5 to 50 mm Terephthalamide short fiber.

(3) The polyparaphenylene terephthalamide short fiber according to any one of (1) to (2) above, wherein the alkali ion content is 0.5% by weight or less.

(4) The polyparaphenylene terephthalamide short fiber according to any one of (1) to (3) above, wherein the water content is 15 to 100% by weight.

(5) A polyparaphenylene terephthalamide short fiber characterized in that the alkali fiber content is 0.2% by weight or less by deionizing the short fiber according to any one of (1) to (4) above. .

(6) A polyparaphenylene terephthalamide short fiber having a crystal size of 50 angstroms or more by heat-treating the fiber described in (5) above.

(7) The polyparaphenylene terephthalamide short fiber according to any one of the above (1) to (6), wherein the alkali ion is an ion selected from Na +, K +, Mg2 +, Ca2 +, and NH4 +.

(8) An insulating / low dielectric material characterized by using the polyparaphenylene terephthalamide short fiber described in (5) or (6) above.

(9) A resin composite comprising the polyparaphenylene terephthalamide short fiber described in (5) or (6) above.

(10) A rubber composite using the polyparaphenylene terephthalamide short fiber described in (5) or (6) above.

(11) A sheet-like structure for a printed wiring board, characterized in that the polyparaphenylene terephthalamide short fiber described in (5) or (6) above is used.

  The PPTA fiber before heat treatment of the present invention can be further reduced in Na + content by deionization treatment. Moreover, the PPTA fiber after heat treatment has a small Na + content and is useful for various applications.

  The polyparaphenylene terephthalamide (PPTA) in the present invention is a polymer obtained by polycondensation of terephthalic acid and paraphenylene diamine, but a polymer obtained by copolymerizing a small amount of dicarboxylic acid and diamine can also be used. Or, the molecular weight of the copolymer is usually preferably 20,000 to 25,000.

  PPTA fibers are made by dissolving PPTA in concentrated sulfuric acid, extruding the viscous solution from a spinneret, spinning into air or water, neutralizing with an aqueous sodium hydroxide solution, and finally Is obtained by drying and heat treatment at 120 to 500 ° C. The PPTA fiber before drying / heat treatment has a crystal size (110 face) of 50 angstroms or less, and usually exceeds 50 angstroms after drying / heat treatment.

  The PPTA short fiber before heat treatment, which is one of the present invention, needs to have a short fiber crystal size of 50 angstroms or less and an alkali ion content of 1.0% or less. When the crystal size exceeds 50 angstroms, it becomes difficult to extract alkali ions. On the other hand, if the alkali ion content exceeds 1.0%, the application to the electric / electronic field, which is the object of the present invention, is limited. And preferably crystal | crystallization size is 35-45 angstrom, and alkali ion content is 0.5 weight% or less.

  Moreover, it is preferable that the water content of the PPTA short fiber before the heat treatment of the present invention is maintained at 15 to 100% by weight. In order to obtain such a moisture content, it is preferable to dry the spun PPTA fiber at 100 to 150 ° C. for 5 to 20 seconds at a low temperature. If the drying temperature is less than 100 ° C., it is difficult to remove moisture, and if it exceeds 150 ° C., crystallization proceeds and subsequent deionization tends to be impossible. The fiber thus obtained is cut or fibrillated with a cutter or the like so as to have an aspect ratio of 50 to 5000, and the intended PPTA short fiber is obtained.

  In the present invention, the PPTA short fibers having such physical properties before heat treatment are deionized. The conditions for the deionization treatment are not particularly limited, but it is usually preferable to wash or extract with water or warm water. The alkali ion content of the deionized PPTA short fiber is preferably 0.2% by weight or less. The PPTA short fiber thus obtained can be heat treated at a temperature of 150 to 500 ° C. to make the crystal size 50 angstroms or more.

  Therefore, the PPTA short fiber after heat treatment, which is one of the present invention, has a crystal size of 50 angstroms or more and an alkali ion content of 0.2% by weight or less.

As a typical example of the method for producing the PPTA short fiber of the present invention, PPTA is dissolved in concentrated sulfuric acid to obtain a viscous solution of 18 to 20% by weight, and this is discharged from the spinneret, and in the air for a short time. Spin into water and spin into water. At this time, it is preferable to set the shear rate during discharge of the die to 25,000 to 50,000 sec ⁻¹ . Thereafter, the fiber solidified in the spinning bath is neutralized with an aqueous sodium hydroxide solution, and then dried at 100 to 150 ° C., preferably for 5 to 20 seconds. The fiber thus obtained is cut or fibrillated with a cutter or the like so as to have an aspect ratio of 50 to 5000, and the intended PPTA short fiber is obtained. Thus, the PPTA short fiber before heat treatment of the present invention is obtained. Thereafter, the short fibers before the heat treatment are extracted with water, deionized, and heat-treated at a temperature of 150 to 500 ° C. after the alkali ion content becomes 0.2% by weight or less. PPTA short fibers are obtained.

  The PPTA short fiber of the present invention is useful for various applications. First, paper can be obtained by dispersing the PPTA short fibers of the present invention in water together with a binder, and making the paper. Alternatively, it can be used as a paper binder by actively using the fibrillated structure. This paper has excellent properties of PPTA and has a low alkali ion content, so it has excellent insulation and is optimal for electrical and electronic parts.

  In addition, the PPTA short fiber of the present invention is a resin composite, a rubber composite, a spun yarn, a fabric using a spun yarn, a fabric such as a knitted fabric, a non-woven fabric, and a printed wiring board sheet. It is useful for the shape.

  Hereinafter, although an Example is shown, the physical property in an Example followed the following measuring method.

(1) Na + content About 0.5 g of a sample is collected in a platinum dish, dissolved in sulfuric acid, and incinerated with a gas burner and an electric furnace. The obtained ashed product is decomposed by heating with sulfuric acid, nitric acid and hydrofluoric acid, and dissolved in dilute nitric acid to obtain a constant solution. Measurement of Na in the obtained constant solution is performed by atomic absorption spectrometry.

(2) Water content Approximately 5 g of the sample is weighed, heat-treated at 300 ° C. for 20 minutes, left in a standard state for 5 minutes, and then weighed again. The moisture content used here is the dry base moisture content obtained by [weight before drying−weight after drying] / [weight after drying].

(3) Crystal size A sample is prepared to have a length of 4 cm and a weight of 20 mg, and is hardened with a collodion solution. Next, data is collected using a wide-angle X-ray diffraction (diffractometer) method. Of the obtained 2θ / θ intensity data, calculation is made from the half width of the surface in the 110 direction using the Scherrer equation.

Example 1
1 kg of PPTA (molecular weight of about 20,000) obtained by a normal method is dissolved in 4 kg of concentrated sulfuric acid, and discharged from a die having 1000 holes with a diameter of 0.1 mm so as to have a shear rate of 30,000 sec-1. After spinning in water at 4 ° C, neutralization with 10% aqueous sodium hydroxide was performed at 10 ° C for 15 seconds, followed by low temperature drying at 110 ° C for 15 seconds. The cut fiber was cut with a cutter to an aspect ratio of 300 to obtain a short PPTA fiber before heat treatment.

  Table 1 shows the properties of the PPTA short fibers before the heat treatment.

  The PPTA short fibers were extracted with water under conditions of 20 ° C. × 1 hour, deionized, and then heat-treated at 400 ° C. × 30 seconds. Table 1 shows the physical properties of the PPTA short fibers after the heat treatment.

Comparative Example 1
Immediately after the neutralization treatment, low-temperature drying was not performed, and the same heat treatment as in Example 1 was performed. The physical properties of the obtained PPTA fiber are shown in Table 1.

Example 2
Using the PPTA fibers obtained in Example 1 and Comparative Example 1, paper was produced by a known method and used as a printed wiring board sheet. As a result, although the thing of Example 1 showed the outstanding insulation and durability, the thing of the comparative example 1 had a problem in insulation.

表１の結果から、ＰＰＴＡ繊維を熱処理する前に、脱イオン処理することにより、Ｎａ＋含有量を減らし、絶縁性に優れたＰＰＴＡ繊維を得ることができることがわかる。

From the results of Table 1, it can be seen that PPTA fibers having excellent insulating properties can be obtained by reducing the Na + content by subjecting the PPTA fibers to heat treatment before heat treatment.

Claims (11)

A short polyparaphenylene terephthalamide having a crystal size (110 plane) of 50 angstroms or less, an alkali ion content of 1.0% by weight or less, a diameter of 1 to 20 μm, and an aspect ratio of 50 to 5000 fiber. Short polyparaphenylene terephthalamide characterized by having a crystal size (110 plane) of 50 angstroms or less, an alkali ion content of 1.0% by weight or less, and a fibrillation length of 0.5 to 50 mm fiber. The polyparaphenylene terephthalamide short fiber according to any one of claims 1 to 2, wherein the alkali ion content is 0.5% by weight or less. The polyparaphenylene terephthalamide short fiber according to any one of claims 1 to 3, wherein the water content is 15 to 100% by weight. A polyparaphenylene terephthalamide short fiber characterized in that the alkali ion content is 0.2% by weight or less by deionizing the short fiber according to any one of claims 1 to 4. A polyparaphenylene terephthalamide short fiber characterized in that the crystal size is made 50 angstroms or more by heat-treating the fiber according to claim 5. 7. The polyparaphenylene terephthalamide short fiber according to claim 1, wherein the alkali ion is an ion selected from Na +, K +, Mg2 +, Ca2 +, and NH4 +. An insulating and low dielectric material using the polyparaphenylene terephthalamide short fiber according to claim 5 or 6. A resin composite comprising the polyparaphenylene terephthalamide short fiber according to claim 5 or 6. A rubber composite comprising the polyparaphenylene terephthalamide short fiber according to claim 5 or 6. A sheet-like structure for a printed wiring board, characterized in that the polyparaphenylene terephthalamide short fiber according to claim 5 or 6 is used.