JP3702979B2 - Black polybenzazole fiber - Google Patents

Description

【０００７】
【化２】

【０００８】
ＰＢＺポリマーのドープを形成するための好適な溶媒としては、クレゾールやそのポリマーを溶解し得る非酸化性の酸が含まれる。好適な酸溶媒の例としては、ポリリン酸、メタンスルホン酸および高濃度の硫酸あるいはそれらの混合物が挙げられる。さらに適する溶媒はポリリン酸及びメタンスルホン酸である。また最も適する溶媒は、ポリリン酸である。
【０００９】
溶媒中のポリマー濃度は好ましくは少なくとも約７重量％であり、さらに好ましくは少なくとも１０重量％、最も好ましくは少なくとも１４重量％である。最大濃度は、例えばポリマーの溶解性やドープ粘度といった実際上の取扱い性により限定される。それらの限界要因のために、ポリマー濃度は通常では２０重量％を超えることはない。
【００１０】
好適なポリマーやコポリマーあるいはドープは公知の手法により合成される。例えばWolfe 等の米国特許第４５３３６９３号（１９８５年８月６日）、Sybert等の米国特許４７７２６７８号（１９８８年９月２０日）、Harrisの米国特許第４８４７３５０号（１９８９年７月１１日）に記載される方法で合成される。ＰＢＺポリマーは、Gregory 等の米国特許第５０８９５９１号（１９９２年２月１８日）によると、脱水性の酸溶媒中での比較的高温、高剪断条件下において高い反応速度での高分子量化が可能である。
【００１１】
このようにして重合されるドープに有機炭化物に炭化しうる有機物をを０．１〜５重量％、さらに好ましくは０．２〜３重量％添加し均一に混合した後、紡糸部に供給され、紡糸口金から通常１００℃以上の温度で吐出される。尚、本発明で言う有機炭化物とは有機化合物を炭化することにより得られる物質を言うが、本発明の目的とする繊維の遮光効果をを最も直接的かつ効果的に達成するには、カーボンブラックが望ましい。またかかる目的を工業的手段を用いて合理的に達成するには、米国特許第5089591 号記載の方法のように、二軸の混練機を用る場合、重合時にテレフタル酸等のジカルボン酸又はその誘導体のポリリン酸溶液を添加するに際し、下記式で示すＰＢＺモノマ−に対し過剰のジカルボン酸を添加して重合し、その後重合ドープを紡糸し、繊維の熱処理工程において未反応の過剰ジカルボン酸を黒色の有機炭化物に炭化させて遮光剤とする方法も採用できる。この場合O-アミノフェノ−ル等の末端封鎖剤を用いて重合度或いは未反応の過剰ジカルボン酸残量を調整してもよい。特にこの方法の利点は、モノマ−の仕込み比率を変更するのみで本発明の目的を達成することができる点にある。
なお、ジカルボン酸を下記式で示すモノマ−に対し1.005 〜1.25モル％の割合で重合するのが好ましい。
【００１２】
【化３】

【００１３】
紡糸に用いる、口金細孔の配列は通常円周状、格子状に複数個配列されるが、その他の配列であってもよい。口金細孔数は特に限定されないが、紡糸口金面における紡糸細孔の配列は、吐出糸条間の融着などが発生しないような孔密度を保つ必要がある。
該紡糸口金から非凝固性の気体中（いわゆるエアーギャップ）に吐出されたフィラメント状のドープはエアーギャップ中でドラフトを与えられる。該糸条の冷却効率を高めるためエアーギャップ中に、冷却風を用いて糸条を冷却するいわゆるクエンチチェンバーを設けることは特に早い紡糸速度を得るためには有効である。
【００１４】
ついで該糸条は凝固液に導かれ凝固およびまたは抽出される。凝固浴はリン酸水溶液若しくは水が好ましく、１０〜３０％の濃度のリン酸水溶液がさらに好ましい。凝固浴の温度は０〜８０℃が好ましく、更に好ましくは３０〜７０℃である。
【００１５】
この条件下に０．０２〜１０秒の凝固を行った後さらに水洗する。水洗後のリン濃度は１００００ｐｐｍ以下、好ましくは５０００ｐｐｍ以下が好ましい。水洗後該繊維はアルカリ金属を含む塩基性化合物の水溶液で処理される。アルカリ金属化合物としてはNaI 、NaOH、KOH 、LiOHなどが好ましく、なかんずく工業的に安価なためNaOHが特に好ましい。もちろん化合物としてはアルカリ金属を含む塩基であれば上記に限定するものではない。
【００１６】
該繊維とアルカリ金属塩基との接触は、凝固以降の工程であればどこでも良いが、乾燥前の繊維は繊維中にボイド（キャピラリー）が連続した状態で存在するため、該アルカリ金属化合物に起因するイオンが繊維中に速やかに拡散することから乾燥前での処理が最も好適である。
【００１７】
繊維中に侵入するアルカリ金属はリン酸残渣と会合するため通常繊維中に残存するリンに対し０．５〜２．５倍の原子比率を示すことが、耐湿熱劣化性を改良する目的に必要である。中和された繊維は再度水洗され、ついで乾燥される。
【００１８】
乾燥された繊維がすでに黒色を呈するものはそのままでよいが、有機物が炭化前駆体である場合は、前駆体を炭化するため熱処理される。熱処理温度は５５０〜７５０℃でかつ酸素を含有する雰囲気で行われる。特に酸素量を増加させる必要はなく空気雰囲気でよい。温度は好ましくは６００〜７００℃である。炭化過程はベンザゾール繊維が熱処理中に赤色に変化するにもかかわらず糸切れが発生せず、不思議な光景である。熱処理後の糸は黒色に変化しており、少なくとも繊維表面から繊維外層部にかけて炭化有機物を含有すものであった。
【００１９】
【実施例】
以下に実施例を示すが本発明はこれらの実施例に限定されるものではない。
＜実施例１＞
米国特許５０８９５９１号示す方法により、３０φの二軸エクストルーダ（真空ベント付き）を用いて重合するに際し、あらかじめ２モル％過剰にジアミノレゾルシン塩酸塩を仕込み、二軸エクストルーダ重合時に３モル％のテレフタル酸を７％リン酸溶液として添加し、さらにo-アミノフェノールを１．５モル％添加して重合を完了させ、ドープ温度を１７０℃に保ち、孔数１６６を有する紡糸口金から１７０℃で紡出し、温度６０℃の冷却風を用いて吐出糸条を冷却した後、凝固浴中に導入した。紡糸速度、凝固浴温度および凝固浴のリン酸水溶液濃度は表１に示す条件とした。凝固に引き続いて第二の抽出浴中でイオン交換水で糸条を洗浄した後、０．１規定の水酸化ナトリウム溶液浸漬し中和処理した。さらに水洗浴で洗浄した後、乾燥機を用いて直ちに乾燥を行った。乾燥した糸条は６５０℃で５秒間熱処理しテレフタル酸の残滓を炭化し、黒色の繊維を得た。得られた繊維の物性を同じく表１に示す。
【００２０】
＜実施例２＞
米国特許５０８９５９１号示す方法により、30φの二軸エクストルーダ（真空ベント付き）を用いて重合するに際し、あらかじめ２モル％過剰にテレフタル酸を仕込み二軸エクストルーダ重合時に１．５モル％ジアミノレゾルシンリン酸塩の７％リン酸溶液として添加して重合を完了させ、ドープ温度を１７０℃に保ち、孔数１６６を有する紡糸口金から１７０℃で紡出し、温度６０℃の冷却風を用いて吐出糸条を冷却した後、凝固浴中に導入した。紡糸速度、凝固浴温度および凝固浴のリン酸水溶液濃度は表１に示す条件とした。凝固に引き続いて第二の抽出浴中でイオン交換水で糸条を洗浄した後、０．１規定の水酸化ナトリウム溶液浸漬し中和処理した。さらに水洗浴で洗浄した後、乾燥機を用いて直ちに乾燥を行った。乾燥した糸条は 650℃で５秒間熱処理しテレフタル酸の残滓を炭化し、黒色の繊維を得た。繊維の物性を同じく表１に示す。
【００２１】
＜比較例１＞
米国特許５０８９５９１号示す方法により、３０φの二軸エクストルーダ（真空ベント付き）を用いて重合するに際し、あらかじめ２モル％過剰にジアミノレゾルシン塩酸塩を仕込み、二軸エクストルーダ重合時に１．８モル％のテレフタル酸を７％ポリリン酸溶液として添加し、さらにカーボンブラックの７％ポリリン酸溶液を７wt％添加して重合を完了させ、ドープ温度を１７０℃に保ち、孔数１６６を有する紡糸口金から１７０℃で紡出し、温度６０℃の冷却風を用いて吐出糸条を冷却した後、凝固浴中に導入した。紡糸速度、凝固浴温度および凝固浴のリン酸水溶液濃度は表１に示す条件とした。凝固に引き続いて第二の抽出浴中でイオン交換水で糸条を洗浄した後、０．１規定の水酸化ナトリウム溶液浸漬し中和処理した。さらに水洗浴で洗浄した後、乾燥機を用いて直ちに乾燥を行った。繊維の物性を同じく表１に示す。
【００２２】
＜比較例２＞
カーボンブラックを添加しないことおよび中和処理を行わないこと以外は実施例３の方法により黄金色の繊維を比較例として得た。得られた繊維の物性を表１に示す。
【００２３】
実施例１〜２および比較例１〜２の繊維の耐光試験および耐湿熱試験を行った。 耐光試験はキセノンランプを用いたウエザオメータ（アトラス社、形式Ci35A ）で行い、繊維をニット・デニットした資料をサンプルホルダーにセットして83℃で24時間照射した後、強度の保持率を測定した。また湿熱試験はオートクレーブを用いて 180℃の飽和水蒸気中に30時間暴露し、暴露後の強度保持率を測定した。それらの結果を同じく表１に示す。この表で明らかなように、本発明による黒色の繊維は従来技術によるものに比べ、初期の物性の低下もなくかつ耐光性、耐湿熱性が顕著に改善されている事が認められる。本発明の技術によりより少ない設備投資により極めて効率的に係るポリベンザゾール繊維が製造できることを明らかにした。
【００２４】
【表１】

【００２５】
【発明の効果】
本発明により、耐光性・耐湿熱性に優れた黒色のポリベンザゾール繊維が工業的規模で容易に製造することを可能とした。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to black polybenzazole fibers having high strength and high elastic modulus. More specifically, the present invention relates to a high-strength and high-modulus polybenzoxazole fiber excellent in heat and moisture resistance and light resistance.
[0002]
[Prior art]
Polybenzazole fiber has a strength and an elastic modulus more than twice that of polyparaphenylene terephthalamide fiber, which is a representative super fiber currently on the market. Therefore, it is expected as a next-generation super fiber. It is known to produce fibers from polyphosphoric acid solutions of polybenzazole polymers. For example, the spinning method is disclosed in JP-A-7-157918 and JP-A-7-157919, the drying method is disclosed in JP-A-7-197307, and the heat treatment method is disclosed in JP-A-7-15920. Each of which is disclosed in the Gazette. However, the excellent mechanical properties are not without weak points, and the wet heat and light resistance are inferior to other properties. For this reason, neutralization of phosphoric acid residues is effective in improving wet heat characteristics, and Japanese Patent Application No. 7-251137 discloses that various light-resistant agents are effective as methods for improving light resistance. This is proposed in Japanese Patent No. 5552221.
[0003]
[Problems to be solved by the invention]
According to the prior art, in order to produce a polybenzazole fiber having excellent mechanical properties and excellent light resistance and heat and humidity resistance, the number of processes is large and complicated, and thus a huge capital investment is required. The present invention provides a polybenzazole fiber that overcomes such technical difficulties, has excellent mechanical properties and is excellent in light resistance and moisture and heat resistance, and can be stably supplied at a relatively low cost. To do.
[0004]
[Means for Solving the Problems]
The inventors of the present invention aimed to produce polybenzazole fibers excellent in moisture and heat resistance and light resistance at high speed and at low cost, and as a result of earnest research to achieve such purposes, have found a solution. That is, it is effective to block visible light to improve the light resistance of polybenzazole, neutralization of residual phosphoric acid is effective to improve the heat and moisture resistance, especially when the neutralizing agent contains an alkali metal. It has been found that it is also effective in improving light resistance. Means for this purpose include organic carbides or their precursors that finally exhibit a black color, and a spinning dope consisting essentially of polybenzazole and polyphosphoric acid is melt-spun out of the spinneret and is usually non-solidified, called an air gap. After the draft is applied to the yarn in a natural gas, it is solidified and / or extracted. In the process after the extraction, it is a production method in which treatment is performed with an aqueous solution containing an alkali metal compound, and heat treatment is performed as necessary after drying.
[0005]
The present invention will be described in detail below.
The polybenzazole fiber in the present invention refers to a fiber made of a polybenzazole polymer, and the polybenzazole (PBZ) is a polybenzoxazole (PBO) homopolymer, a polybenzothiazole (PBT) homopolymer, and their PBO, PBT random, sequential or block copolymer. Here, polybenzoxazole, polybenzothiazole and their random, sequential or block copolymer are disclosed in, for example, Wolfe et al., “Liquid Crystalline Polymer Compositions, Process and Products” US Pat. No. 4,703,103 (October 27, 1987), “Liquid Crystall-ine Polymer Compositions, Process and Products”, US Pat. No. 4,533,692 (August 6, 1985), “Liquid Crystalline Poly (2,6-Benzothiazole) Composition, Process and Products”, US Pat. No. 4,533,724 (1985) August 6), “Liquid Crystalline Polymer Compositions, Process and Products” US Pat. No. 4,533,693 (August 6, 1985), Evers “Thermoox idative-lyStable Articulated p-Benzobisoxazole and p-Benzobisthiazole Polymres” US Pat. 4359567 (November 16, 1982), Tasi et al., “Method for making Heterocyclic Block Copolymer ", U.S. Pat. No. 4,578,432 (March 25, 1986), and the like.
The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers. The monomer unit consists of monomer units described in structural formulas (a) to (h), and more preferably consists essentially of monomer units selected from structural formulas (a) to (d).
[0006]
[Chemical 1]

[0007]
[Chemical formula 2]

[0008]
Suitable solvents for forming the PBZ polymer dope include cresol and a non-oxidizing acid capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and high concentrations of sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.
[0009]
The polymer concentration in the solvent is preferably at least about 7% by weight, more preferably at least 10% by weight, and most preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration usually does not exceed 20% by weight.
[0010]
Suitable polymers, copolymers or dopes are synthesized by known techniques. For example, Wolfe et al., U.S. Pat. No. 4,533,693 (August 6, 1985), Sybert et al., U.S. Pat. No. 4,772,678 (September 20, 1988), Harris, U.S. Pat. No. 4,847,350 (July 11, 1989). Synthesized by the method described. PBZ polymers, according to US Pat. No. 5,089,591 (February 18, 1992) by Gregory et al., Can achieve high molecular weights at high reaction rates under relatively high temperature and high shear conditions in dehydrating acid solvents. It is.
[0011]
An organic substance that can be carbonized into an organic carbide is added to the dope thus polymerized in an amount of 0.1 to 5% by weight, and more preferably 0.2 to 3% by weight. It is normally discharged from the spinneret at a temperature of 100 ° C. or higher. The organic carbide referred to in the present invention refers to a substance obtained by carbonizing an organic compound. In order to achieve the fiber shading effect of the present invention most directly and effectively, carbon black is used. Is desirable. In order to achieve such an object reasonably by using industrial means, when a biaxial kneader is used, as in the method described in US Pat. No. 5,889,591, a dicarboxylic acid such as terephthalic acid or the like during polymerization is used. When adding the polyphosphoric acid solution of the derivative, an excess dicarboxylic acid is added to the PBZ monomer represented by the following formula to polymerize, and then the polymerization dope is spun and unreacted excess dicarboxylic acid is blackened in the fiber heat treatment step. A method of carbonizing the organic carbide to form a light shielding agent can also be adopted. In this case, the degree of polymerization or the remaining amount of unreacted excess dicarboxylic acid may be adjusted by using a terminal blocking agent such as O-aminophenol. In particular, the advantage of this method is that the object of the present invention can be achieved only by changing the monomer charging ratio.
The dicarboxylic acid is preferably polymerized at a ratio of 1.005 to 1.25 mol% with respect to the monomer represented by the following formula.
[0012]
[Chemical 3]

[0013]
A plurality of die pore arrays used for spinning are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of nozzle holes is not particularly limited, but the arrangement of the spinning holes on the spinneret surface needs to maintain a hole density that does not cause fusion between discharged yarns.
The filamentous dope discharged from the spinneret into a non-solidifying gas (so-called air gap) is given a draft in the air gap. In order to increase the cooling efficiency of the yarn, it is effective to provide a so-called quench chamber that cools the yarn using cooling air in the air gap in order to obtain a particularly high spinning speed.
[0014]
The yarn is then guided to the coagulation liquid and coagulated and / or extracted. The coagulation bath is preferably an aqueous phosphoric acid solution or water, and more preferably an aqueous phosphoric acid solution having a concentration of 10 to 30%. The temperature of the coagulation bath is preferably 0 to 80 ° C, more preferably 30 to 70 ° C.
[0015]
Under this condition, 0.02 to 10 seconds of coagulation is carried out, followed by washing with water. The phosphorus concentration after washing with water is 10,000 ppm or less, preferably 5000 ppm or less. After washing with water, the fiber is treated with an aqueous solution of a basic compound containing an alkali metal. As the alkali metal compound, NaI, NaOH, KOH, LiOH and the like are preferable, and NaOH is particularly preferable because it is industrially inexpensive. Of course, the compound is not limited to the above as long as it is a base containing an alkali metal.
[0016]
The contact between the fiber and the alkali metal base may be anywhere as long as it is a step after the coagulation, but the fiber before drying is caused by the alkali metal compound because voids (capillaries) are continuously present in the fiber. The treatment before drying is most preferred because ions diffuse quickly into the fiber.
[0017]
Alkali metal that penetrates into the fiber is associated with phosphoric acid residue, so it is usually necessary to improve the resistance to moist heat resistance by showing an atomic ratio of 0.5 to 2.5 times that of phosphorus remaining in the fiber. It is. The neutralized fiber is washed again with water and then dried.
[0018]
If the dried fiber already exhibits a black color, it may be left as it is, but if the organic material is a carbonized precursor, it is heat treated to carbonize the precursor. The heat treatment temperature is 550 to 750 ° C. and an atmosphere containing oxygen. In particular, it is not necessary to increase the amount of oxygen, and an air atmosphere is sufficient. The temperature is preferably 600 to 700 ° C. The carbonization process is a strange sight because yarn breakage does not occur despite the benzazole fiber turning red during heat treatment. The yarn after the heat treatment changed to black and contained a carbonized organic substance at least from the fiber surface to the fiber outer layer portion.
[0019]
【Example】
Examples are shown below, but the present invention is not limited to these Examples.
<Example 1>
According to the method shown in US Pat. No. 5,089,591, when polymerizing using a 30φ biaxial extruder (with a vacuum vent), diaminoresorcin hydrochloride was charged in excess of 2 mol% in advance, and 3 mol% of terephthalic acid was added during biaxial extruder polymerization. 7% phosphoric acid solution was added, and 1.5 mol% of o-aminophenol was added to complete the polymerization, and the dope temperature was kept at 170 ° C., and the spinneret having a pore number of 166 was spun at 170 ° C., The discharged yarn was cooled using cooling air having a temperature of 60 ° C. and then introduced into the coagulation bath. The spinning speed, coagulation bath temperature, and concentration of phosphoric acid aqueous solution in the coagulation bath were as shown in Table 1. Subsequent to coagulation, the yarn was washed with ion-exchanged water in the second extraction bath and then immersed in a 0.1N sodium hydroxide solution for neutralization. Further, after washing in a water bath, drying was performed immediately using a dryer. The dried yarn was heat-treated at 650 ° C. for 5 seconds to carbonize the residue of terephthalic acid to obtain black fibers. The physical properties of the obtained fiber are also shown in Table 1.
[0020]
<Example 2>
According to the method shown in US Pat. No. 5,089,591, terephthalic acid was previously added in an excess of 2 mol% when polymerizing using a 30φ biaxial extruder (with a vacuum vent), and 1.5 mol% diaminoresorcin phosphate was added during the biaxial extruder polymerization. Is added as a 7% phosphoric acid solution to complete the polymerization, the dope temperature is maintained at 170 ° C., spinning is performed at 170 ° C. from a spinneret having a hole number of 166, and a discharge yarn is formed using cooling air at a temperature of 60 ° C. After cooling, it was introduced into a coagulation bath. The spinning speed, coagulation bath temperature, and concentration of phosphoric acid aqueous solution in the coagulation bath were as shown in Table 1. Subsequent to coagulation, the yarn was washed with ion-exchanged water in the second extraction bath and then immersed in a 0.1N sodium hydroxide solution for neutralization. Further, after washing in a water bath, drying was performed immediately using a dryer. The dried yarn was heat treated at 650 ° C. for 5 seconds to carbonize the residue of terephthalic acid to obtain black fibers. The physical properties of the fiber are also shown in Table 1.
[0021]
< Comparative Example 1 >
According to the method shown in US Pat. No. 5,089,591, diaminoresorcin hydrochloride is charged in excess of 2 mol% in advance when polymerization is performed using a 30φ biaxial extruder (with a vacuum vent), and 1.8 mol% of terephthalate is formed during biaxial extruder polymerization. The acid was added as a 7% polyphosphoric acid solution, and further 7 wt% of a 7% polyphosphoric acid solution of carbon black was added to complete the polymerization, the dope temperature was kept at 170 ° C., and the spinneret having a pore number of 166 Spinning and cooling the discharged yarn using cooling air having a temperature of 60 ° C., the mixture was introduced into a coagulation bath. The spinning speed, coagulation bath temperature, and concentration of phosphoric acid aqueous solution in the coagulation bath were as shown in Table 1. Subsequent to coagulation, the yarn was washed with ion-exchanged water in the second extraction bath and then immersed in a 0.1N sodium hydroxide solution for neutralization. Further, after washing in a water bath, drying was performed immediately using a dryer. The physical properties of the fiber are also shown in Table 1.
[0022]
< Comparative example 2 >
A golden fiber was obtained as a comparative example by the method of Example 3 except that no carbon black was added and no neutralization treatment was performed. Table 1 shows the physical properties of the obtained fiber.
[0023]
The light resistance test and wet heat resistance test of the fibers of Examples 1-2 and Comparative Examples 1-2 were performed. The light resistance test was conducted with a weatherometer using a xenon lamp (Atlas Co., Ltd., type Ci35A). A material knit / denited with fibers was set on a sample holder and irradiated at 83 ° C. for 24 hours, and the strength retention rate was measured. In addition, the wet heat test was carried out using an autoclave in 180 ° C. saturated steam for 30 hours, and the strength retention after the exposure was measured. The results are also shown in Table 1. As is apparent from this table, it can be seen that the black fibers according to the present invention have no significant deterioration in the initial physical properties and light resistance and moist heat resistance are significantly improved as compared with those according to the prior art. It has been clarified that the polybenzazole fiber can be produced very efficiently with less capital investment by the technology of the present invention.
[0024]
[Table 1]

[0025]
【The invention's effect】
The present invention makes it possible to easily produce black polybenzazole fibers excellent in light resistance and heat-and-moisture resistance on an industrial scale.

Claims (1)

A fiber in which dicarboxylic acid and / or a derivative thereof is mixed with a polybenzazole polymer is heat-treated at a temperature of 550 to 750 ° C. in an oxygen-containing atmosphere, and contains a carbonized organic substance at least from the fiber surface to the fiber outer layer portion. A method for producing black polybenzazole fiber , which is characterized .