JP2006207097A - Method for producing polytetrafluoroethylene fiber having small fineness and fabric using the same - Google Patents

Method for producing polytetrafluoroethylene fiber having small fineness and fabric using the same Download PDF

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JP2006207097A
JP2006207097A JP2005024416A JP2005024416A JP2006207097A JP 2006207097 A JP2006207097 A JP 2006207097A JP 2005024416 A JP2005024416 A JP 2005024416A JP 2005024416 A JP2005024416 A JP 2005024416A JP 2006207097 A JP2006207097 A JP 2006207097A
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JP4396536B2 (en
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Katsumi Takehara
勝己 竹原
Tomio Kuwajima
富夫 桑嶋
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Toray Industries Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably producing a uniform PTFE fiber having a round or flat cross section and ≤3.3dtex, which has not been obtained conventionally, by a matrix spinning method and to obtain a fabric having excellent fine dust catching property by using the obtained PTFE fiber having a small fineness. <P>SOLUTION: The method for producing a PTFE fiber having a round or flat fiber cross section and ≤3.3dtex by a matrix spinning method comprises discharging a mixed liquid of a viscose as a matrix and a water dispersion of PTFE from a plurality of nozzle holes to a coagulation bath adjusted to specific components and concentration and spinning the mixed solution. Especially in firing, firing is carried out at a specific temperature after a semi-firing process at a specific temperature while relaxing at a specified relaxation ratio. The fabric having excellent fine dust catching property is obtained by using the uniform PTFE fiber having a small fineness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、マトリックス紡糸法により得られる繊度が均一で且つ細繊度である丸形断面もしくは扁平断面を有するポリテトラフルオロエチレン繊維の製造方法に関する。また、この繊維、この繊維を用いた布帛、この布帛を用いたフィルター用材料または微粒子封止用材料に関する。   The present invention relates to a method for producing a polytetrafluoroethylene fiber having a round cross section or a flat cross section having a uniform fineness and a fineness obtained by a matrix spinning method. The present invention also relates to the fiber, a fabric using the fiber, a filter material or a fine particle sealing material using the fabric.

ポリテトラフルオロエチレン(以下、PTFEと略称する)繊維に代表されるフッ素樹脂系繊維は、その優れた耐熱性、耐薬品性、電気特性あるいは低摩擦係数などから、産業資材用途に広く用いられている。   Fluororesin fibers represented by polytetrafluoroethylene (hereinafter abbreviated as PTFE) fibers are widely used in industrial materials because of their excellent heat resistance, chemical resistance, electrical properties, and low friction coefficient. Yes.

PTFEは不溶解性であり、また加熱溶融時に非常に高い溶融粘度を持っている。その製法は、従来公知のマトリックス法(エマルジョン法ともいう)、スプリット剥離法、またはペースト押出法などにより生産される。一方、PTFEを共重合させた共重合系のフッ素系樹脂(4フッ化エチレン−6フッ化プロピレン共重合体(FEP)、4フッ化エチレン− パーフロロアルコキシ基共重合体(PFA) または4フッ化エチレン− オレフィン共重合体(ETFE)など)は溶融紡糸法により生産が可能である。   PTFE is insoluble and has a very high melt viscosity when heated and melted. The production method is produced by a conventionally known matrix method (also called an emulsion method), split peeling method, paste extrusion method or the like. On the other hand, a copolymer-based fluororesin copolymerized with PTFE (tetrafluoroethylene-6-fluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxy group copolymer (PFA) or 4-fluoroethylene). An ethylene-olefin copolymer (ETFE) and the like can be produced by a melt spinning method.

スプリット剥離法による異形断面PTFE繊維および該異形断面繊維を用いたフェルト状フィルタ材は公知である(特許文献1)。しかし、スプリット剥離法で得られる異形断面繊維はその製法上、どうしても扁平断面形状となり、その形状・繊度もランダムで不均一となるため、フェルト加工時にネップが発生しやすく生産が困難であるという欠点があった。   A modified cross-section PTFE fiber and a felt-shaped filter material using the modified cross-section fiber are known (Patent Document 1). However, the irregular cross-section fiber obtained by the split peeling method has a flat cross-sectional shape due to its manufacturing method, and its shape and fineness are random and non-uniform, so that it is difficult to produce nep during felt processing and difficult to produce was there.

また、共重合タイプのフッ素系樹脂を用いた溶融紡糸による異形断面繊維およびこれを用いたバグフィルタは公知である(特許文献2,3)。しかしながら、溶融紡糸を行う共重合タイプのフッ素系樹脂は溶融時の流動性を与える目的で共重合しているため、どうしてもPTFEに比べ耐薬品性・耐熱性に劣ってしまう。   Also, a modified cross-section fiber by melt spinning using a copolymer type fluororesin and a bag filter using the same are known (Patent Documents 2 and 3). However, since the copolymer-type fluororesin that performs melt spinning is copolymerized for the purpose of providing fluidity at the time of melting, the chemical resistance and heat resistance are inevitably inferior to those of PTFE.

PTFE繊維のエマルジョン法による製法は特許文献4,5により公知である。特許文献4には平均繊度が3d以下の細繊度PTFE繊維が記載されているが、この方法によると、製糸時の糸切れが発生し安定した生産が困難であるという問題があった。特許文献5の方法によっても細繊度PTFE繊維を安定に製造することは困難であった。   The production method of PTFE fiber by the emulsion method is known from Patent Documents 4 and 5. Patent Document 4 describes a fine fineness PTFE fiber having an average fineness of 3d or less. However, according to this method, there is a problem that yarn breakage occurs during yarn production and stable production is difficult. Even with the method of Patent Document 5, it has been difficult to stably produce fineness PTFE fibers.

すなわち、これまで繊度が均一で且つ3.3dex以下の細繊度で安定生産が可能な工業的に実用化可能なPTFE繊維の製造方法は見いだされいなかったのである。   That is, until now, no industrially practical method for producing PTFE fiber that has a uniform fineness and can be stably produced with a fineness of 3.3 dex or less has not been found.

一方で、PTFE繊維は、その用途の中でもゴミ焼却炉のバグフィルター用途に特に広く用いられており、フッ素繊維とガラス繊維との複合品が広く利用されている。あるいはまた、ガラス繊維以外の耐熱性繊維、例えばアラミド、ポリフェニレンサルファイド、ポリイミドあるいはポリパラフェニレンベンゾオキサゾールなどを用いたバグフィルターも広く用いられている。   On the other hand, PTFE fiber is particularly widely used in bag filters for garbage incinerators among its uses, and composite products of fluorine fibers and glass fibers are widely used. Alternatively, bag filters using heat-resistant fibers other than glass fibers, such as aramid, polyphenylene sulfide, polyimide or polyparaphenylene benzoxazole, are also widely used.

上記の耐熱性繊維を用いたバグフィルターに対して、現在はダストの捕集効率がさらに高いバグフィルターが求められている。これは例えばガス化溶融処理炉等に用いられるバグフィルターであり、粒径の小さなダストの捕集が可能な高捕集効率のフィルターである。   In contrast to the bag filter using the above heat-resistant fiber, a bag filter having higher dust collection efficiency is currently required. This is a bag filter used in, for example, a gasification melting furnace and the like, and is a high collection efficiency filter capable of collecting dust having a small particle diameter.

あるいは、また、フッ素樹脂系繊維を用いた微粒子封止材料も広く用いられている。例えばプリンターのトナー封止材料などであり、150℃以上の温度で微少なトナーを封止するものである。トナーのカラー化が進むにつれ、さらに微少なトナーの封止が可能な材料が求められている。   Alternatively, a fine particle sealing material using a fluororesin fiber is also widely used. For example, it is a toner sealing material for a printer and seals a minute amount of toner at a temperature of 150 ° C. or higher. As the colorization of toner progresses, a material capable of encapsulating a finer amount of toner is required.

そこで、耐熱性繊維のフェルト表面にフッ素樹脂の微多孔膜を貼り合わせ、該微多孔膜でダストを高効率に捕集する方法が提案されている(特許文献6)。確かにこの方法では0.5μm以下のダストの捕集効率は高いが、フッ素樹脂の微多孔膜と他素材との接着性が悪いため、剥離してしまうという問題がある。さらにバグフィルター用に使用した場合、逆洗パルスを打つ時にリテーナーと摩擦を生じるため、この摩擦力によっても剥離が発生する問題がある。   Therefore, a method has been proposed in which a fluororesin microporous film is bonded to the felt surface of the heat resistant fiber, and dust is collected with high efficiency by the microporous film (Patent Document 6). Certainly, this method has a high dust collection efficiency of 0.5 μm or less, but has a problem of peeling because the adhesion between the fluororesin microporous film and other materials is poor. Further, when used for a bag filter, there is a problem that separation occurs due to this frictional force because friction occurs with the retainer when a backwash pulse is applied.

あるいは、特許文献7にあるように、極細繊維層とフェルト基材層とをニードルパンチ処理して一体化し、極細化可能繊維の分布を表面から裏面に向かって漸減させ、次に高圧水流パンチによって極細化可能繊維を分割して極細化させるような高捕集効率のフィルターが公知である。しかしこのフィルターでは、2種類以上の異なる繊維を積層する必要があり、加工工程が多い問題がある。さらに、特許文献7の極細化可能繊維はポリアミド/ポリエステルの分割繊維が例示されているにすぎない。   Alternatively, as disclosed in Patent Document 7, the ultrafine fiber layer and the felt base material layer are integrated by needle punching, and the distribution of the ultrafine fiber is gradually reduced from the front surface to the back surface, and then by a high-pressure water punch. A filter with high collection efficiency is known in which a fiber that can be made ultrafine is divided into ultrafine fibers. However, in this filter, it is necessary to laminate two or more kinds of different fibers, and there is a problem that there are many processing steps. Furthermore, the ultrathinnable fiber of Patent Document 7 is only exemplified as a polyamide / polyester split fiber.

また、特許文献8には、分枝及び/またはループを有するフッ素樹脂繊維を用いた濾材が記述されているが、該繊維はカーディング処理してウェッブとした後、ニードルパンチすることで分枝及び/またはループを生じる繊維である。この方法で得られる分枝及び/またはループを有する布帛は、表面および内部、全体にわたってフッ素樹脂繊維が分割しているため、ウェッブの強度が低下する問題がある。
特開2001−276528号公報(特許請求の範囲、第2頁) 特公平3−10723号公報(特許請求の範囲) 特開2002−282627号公報(第3,5,6欄) 登録2571379号公報(特許請求の範囲、第4頁) 登録3327027号公報(特許請求の範囲、第3,4頁) 特開2000−140588号公報等(特許請求の範囲) 特開平4−32649号公報(特許請求の範囲) 特開2000−61224号公報(特許請求の範囲)
In addition, Patent Document 8 describes a filter medium using a fluororesin fiber having branches and / or loops, and the fiber is branched by needle punching after being carded to form a web. And / or fibers that produce loops. The fabric having branches and / or loops obtained by this method has a problem that the strength of the web is lowered because the fluororesin fibers are divided on the entire surface and inside.
JP 2001-276528 A (Claims, page 2) Japanese Patent Publication No. 3-10723 (Claims) JP 2002-282627 A (3rd, 5th and 6th columns) Registration No. 2571379 (Claims, page 4) Registration No. 3327027 (Claims, pages 3 and 4) Japanese Unexamined Patent Publication No. 2000-140588, etc. (Claims) JP-A-4-32649 (Claims) JP 2000-61224 A (Claims)

本発明の課題は、丸形もしくは扁平断面を有する3.3dtex以下の均一なPTFE繊維をマトリックス紡糸法により安定して得る方法を提供することにある。更に、本発明で得られた細繊度PTFE繊維を用いると、より微小なダストの捕集性に優れた布帛を得ることができる。   An object of the present invention is to provide a method for stably obtaining a uniform PTFE fiber having a round shape or a flat cross section of 3.3 dtex or less by a matrix spinning method. Furthermore, when the fineness PTFE fiber obtained in the present invention is used, a fabric excellent in the ability to collect finer dust can be obtained.

上記課題を解決するために、次のような手段を採用する。   In order to solve the above problems, the following means are adopted.

すなわち、マトリックスとしてのビスコースとポリテトラフルオロエチレンの水分散液との混合液を、硫酸濃度7〜13%、硫酸ソーダ濃度7〜15%を含有する凝固浴中に複数の口金孔から吐出し、紡糸、精練した後、焼成ローラ間で1〜5%のリラックスを与えながら80以上320℃未満の温度で半焼成した後、320〜380℃の温度で焼成を行ない、一旦巻き取るか、もしくはそのまま延伸して繊度が3.3dtex以下でかつ繊度ばらつきが10%以下である、丸形断面もしくは扁平断面のポリテトラフルオロエチレン繊維を製造することを特徴とするポリテトラフルオロエチレン繊維の製造方法である。また、本発明に係る布帛は、上記丸形もしくは扁平断面を有し、繊度が均一である細繊度PTFE繊維を用いた布帛であり、更に本発明ではこのような布帛を用いてなるフィルター用材料や微粒子封止材料も提供する。   That is, a mixed liquid of viscose as a matrix and an aqueous dispersion of polytetrafluoroethylene is discharged from a plurality of nozzle holes into a coagulation bath containing a sulfuric acid concentration of 7 to 13% and a sodium sulfate concentration of 7 to 15%. , Spinning, scouring, half firing at a temperature of 80 to less than 320 ° C. while giving relaxation of 1 to 5% between firing rollers, firing at a temperature of 320 to 380 ° C., and winding up once, or A method for producing a polytetrafluoroethylene fiber, characterized by producing a polytetrafluoroethylene fiber having a round cross section or a flat cross section having a fineness of 3.3 dtex or less and a fineness variation of 10% or less. is there. Further, the fabric according to the present invention is a fabric using the fine fineness PTFE fiber having the above-mentioned round shape or flat cross section and having a uniform fineness. Further, in the present invention, a filter material using such a fabric is used. And a particulate encapsulating material.

本発明によれば、これまでになかった丸形もしくは扁平断面を有し、繊度が均一である細繊度PTFE繊維を安定して製造出来、このPTFE繊維を用いると、これまで以上に微少なダストの捕集性に優れた布帛を得ることができる。   According to the present invention, it is possible to stably produce a fine PTFE fiber having a round shape or a flat cross section that has never been obtained and having a uniform fineness. When this PTFE fiber is used, dust that is finer than before can be obtained. It is possible to obtain a fabric excellent in the trapping property.

本発明の方法で得られた繊維を用いると、これまで以上に微小なダストの捕集性に優れた布帛を得ることができる。およびそれをフィブリル化させた布帛はダストの捕集効率が高く、フィルター用材料または微粒子封止用材料用の布帛に好適に用いることができる。   When the fiber obtained by the method of the present invention is used, a fabric excellent in the ability to collect fine dust than ever can be obtained. And the fabric which made it fibrillate has high dust collection efficiency, and can be used suitably for the fabric for filter materials or the material for fine particle sealing.

以下に本発明について、望ましい実施の形態とともに詳細に説明する。   Hereinafter, the present invention will be described in detail together with preferred embodiments.

本発明は、前記課題、つまりPTFE繊維の特性を損なうことなく、より微少なダストの捕集性に優れた布帛について、鋭意検討し、丸形もしくは扁平断面を有する均一な細繊度PTFE繊維を配して構成したところ、かかる課題を一挙に解決することを究明したものである。   The present invention has been intensively studied on the above-mentioned problem, that is, a fabric excellent in the collection property of fine dust without impairing the properties of the PTFE fiber, and arranging a uniform fineness PTFE fiber having a round shape or a flat cross section. As a result, it has been clarified that such problems can be solved all at once.

フッ素系ポリマーにはPTFEの他にPTFEに共重合した4フッ化エチレン−6フッ化プロピレン共重合体(FEP)、4フッ化エチレン−パーフロロアルコキシ基共重合体(PFA)、または4フッ化エチレン− オレフィン共重合体(ETFE)などがあり、これらは溶融紡糸により生産されている。しかしながら、耐熱性の点からPTFEが最も優れている。本発明はこれまで開示されていなかったPTFEからなる丸形もしくは扁平断面を有する形状・繊度が均一な繊維に関するものである。   In addition to PTFE, fluoropolymers include tetrafluoroethylene-6fluoropropylene copolymer (FEP) copolymerized with PTFE, tetrafluoroethylene-perfluoroalkoxy group copolymer (PFA), or tetrafluoride. There are ethylene-olefin copolymers (ETFE) and the like, which are produced by melt spinning. However, PTFE is the most excellent in terms of heat resistance. The present invention relates to a fiber having a uniform shape and fineness having a round or flat cross section made of PTFE, which has not been disclosed so far.

これまでPTFE繊維の製造方法にはマトリックス紡糸法(エマルジョン法ともいう)、スプリット剥離法、ペースト押出法などが知られている。   Conventionally, a matrix spinning method (also called an emulsion method), a split peeling method, a paste extrusion method, and the like are known as methods for producing PTFE fibers.

スプリット剥離法とはPTFEの粉末をシリンダ圧縮せしめた後、焼結、スプリット剥離させた後、延伸する製法である。   The split peeling method is a manufacturing method in which PTFE powder is compressed by cylinder, sintered, split peeled and then stretched.

ペースト押出法とは、マトリックスポリマーを用いずにPTFEの粉末をワックス状潤滑剤と混練し、棒状もしくはフィルム状に成形した後、該潤滑剤を除去し、延伸、焼成(焼成しない場合もある)する製法である。しかしながら、これら2つの製法では、どうしてもその製法上細く切り裂いて得られる最終繊維状物の断面は扁平形状であり、しかもランダムで均一性に劣り、特に短繊維としてフェルト加工する際にはネップなどが生成されやすいという欠点があった。   The paste extrusion method is a method in which PTFE powder is kneaded with a wax-like lubricant without using a matrix polymer, molded into a rod-like or film-like form, then removed, stretched and fired (may not be fired). It is a manufacturing method to do. However, in these two production methods, the final fibrous material obtained by slicing the production method has a flat cross section, and it is random and inferior in uniformity. There was a drawback that it was easily generated.

本発明のいう丸形もしくは扁平断面を有する均一な細繊度PTFE繊維を得るにはマトリックス紡糸法の実施が必要である。マトリックス紡糸法とは、ビスコースなどをマトリックスとしてPTFEの水分散液との混合液を凝固浴中に吐出して繊維化し、次いで精錬した後、焼成を行う。ポリマーの融点以上で焼成することで、マトリックスポリマーの大部分を焼成飛散させながら、PTFEを溶融し、粒子間を融着することで、初めてその後の延伸性が付与される。焼成後、未延伸糸は直接1STEPもしくは2STEPに分けて延伸され、強度が発現する。   In order to obtain a uniform fineness PTFE fiber having a round shape or a flat cross section according to the present invention, it is necessary to carry out a matrix spinning method. In the matrix spinning method, viscose or the like is used as a matrix and a mixed solution of PTFE with an aqueous dispersion of PTFE is discharged into a coagulation bath to be fiberized, and then refined and then fired. By firing at a temperature equal to or higher than the melting point of the polymer, PTFE is melted and the particles are fused while the majority of the matrix polymer is fired and scattered. After firing, the undrawn yarn is drawn directly in 1 STEP or 2 STEP to develop strength.

本発明のいう丸形もしくは扁平断面を有する均一な細繊度PTFE繊維は該マトリックス紡糸法を用い、しかも特定の条件下で製糸を行うことで初めて得られるのであり、スプリット剥離法やペースト押出法で得ることは出来ない。   The uniform fineness PTFE fiber having a round shape or a flat cross-section according to the present invention can be obtained for the first time by using the matrix spinning method and performing yarn production under specific conditions, and can be obtained by a split peeling method or a paste extrusion method. I can't get it.

本発明の均一な細繊度PTFE繊維は、マトリックスとしてビスコースを用い、PTFEの水分散液との混合液を、硫酸濃度7〜13%、硫酸ソーダ濃度7〜15%に制御した凝固浴槽に複数の口金孔から吐出し、紡糸、精練した後、焼成ローラを用い、焼成ローラ間で1〜5%のリラックスを与えながら80以上320℃未満の温度の半焼成工程を経た後に、320〜380℃の温度で焼成を行ない、一旦巻き取るか、もしくはそのまま延伸することが必要である。   The uniform fineness PTFE fiber of the present invention uses viscose as a matrix, and a plurality of mixed liquids of PTFE with an aqueous dispersion are adjusted to a sulfuric acid concentration of 7 to 13% and a sodium sulfate concentration of 7 to 15%. After discharging, spinning, and scouring from the nozzle hole of the nozzle, after using a baking roller and passing through a semi-baking step at a temperature of 80 to less than 320 ° C. while giving a relaxation of 1 to 5% between the baking rollers, 320 to 380 ° C. It is necessary to perform firing at a temperature of 1 mm and wind up or stretch as it is.

本発明で用いるビスコースは通常レーヨン製造に用いられるもの、すなわちセルロース濃度5〜10重量%、アルカリ濃度4〜10%重量%、二硫化炭素27〜32重量%(セルロースに対し)が好ましい。   The viscose used in the present invention is preferably those usually used for rayon production, that is, a cellulose concentration of 5 to 10% by weight, an alkali concentration of 4 to 10% by weight, and carbon disulfide of 27 to 32% by weight (based on cellulose).

本発明で用いるPTFEの水分散液は濃度は50〜70重量%、安定剤として非イオン活性剤またはアニオン活性剤をPTFEポリマに対して3〜10重量%含有するものが好ましく用いられる。またPTFE水分散液の分散粒子の大きさは0.5μm以下、好ましくは0.3μm以下である。   The aqueous dispersion of PTFE used in the present invention preferably has a concentration of 50 to 70% by weight and contains a nonionic or anionic surfactant as a stabilizer in an amount of 3 to 10% by weight based on the PTFE polymer. The size of the dispersed particles of the PTFE aqueous dispersion is 0.5 μm or less, preferably 0.3 μm or less.

これらビスコースとPTFEの水分散液を混合させて混合液を作製する。 この際、混合液中のPTFE濃度は20〜40%、好ましくは25〜35%、一方、セルロース濃度は2〜6%、好ましくは3〜5%程度である。   These viscose and PTFE aqueous dispersions are mixed to prepare a mixed solution. At this time, the PTFE concentration in the mixed solution is 20 to 40%, preferably 25 to 35%, while the cellulose concentration is about 2 to 6%, preferably about 3 to 5%.

この時、PTFE濃度が40%を超えて高すぎると凝固浴中で糸条が凝固しにくくなる。また精練浴・アルカリ浴中で糸条からPTFE粒子が脱落して安定した紡糸が行えなくなってしまう。また、焼成時にPTFE粒子同士の融着が強固となり単糸間融着が激しくなる他、単糸自体のフィブリル化も発現しにくくなるので好ましくない。PTFE濃度が20%未満となると、凝固浴中で凝固はしやすくなるが焼成時に均一な断面形状を保つことが困難になる他、焼成後の繊維中に炭化成分が多く残存するようになるため繊維強度が著しく低下し好ましくない。   At this time, if the PTFE concentration exceeds 40% and is too high, the yarn is difficult to coagulate in the coagulation bath. In addition, PTFE particles fall off from the yarn in a scouring bath / alkaline bath, and stable spinning cannot be performed. Further, it is not preferable because the fusion between the PTFE particles becomes strong at the time of firing and the fusion between the single yarns becomes intense, and the fibrillation of the single yarns itself is hardly exhibited. If the PTFE concentration is less than 20%, it is easy to coagulate in the coagulation bath, but it becomes difficult to maintain a uniform cross-sectional shape during firing, and a large amount of carbonized components remain in the fiber after firing. The fiber strength is undesirably lowered.

この混合された混合液は脱泡されるが、この時温度が高いとビスコースが凝固してしまう懸念、また水分が蒸発しPTFEが凝集する懸念がある。そのため、脱泡時は15℃以下の低温に制御することが好ましい。真空度は約10Torr程度が好ましい。ビスコースとPTFEの混合のタイミングについては脱泡前にビスコースとPTFE水分散液を混合するか、それぞれ脱泡した後スタティックミキサーなどを用い口金に導く直前で混合する方法が採用できる。   The mixed liquid is defoamed, but if the temperature is high at this time, there is a concern that the viscose will solidify, and there is a concern that the moisture evaporates and PTFE aggregates. Therefore, it is preferable to control to a low temperature of 15 ° C. or lower during defoaming. The degree of vacuum is preferably about 10 Torr. Regarding the timing of mixing the viscose and PTFE, a method of mixing the viscose and the PTFE aqueous dispersion before defoaming or mixing them immediately before defoaming and introducing them to a die using a static mixer or the like can be employed.

次に、この紡糸混合液は凝固浴中に浸漬された多数の吐出孔からなる成型用口金より吐出し、凝固される。   Next, the spinning mixture is discharged from a molding die composed of a large number of discharge holes immersed in a coagulation bath and solidified.

凝固浴としては無機鉱酸および/または無機塩の水溶液が用いられるが、本発明では硫酸−硫酸ソーダの混合水溶液を用いる。   As the coagulation bath, an aqueous solution of an inorganic mineral acid and / or an inorganic salt is used. In the present invention, a mixed aqueous solution of sulfuric acid and sodium sulfate is used.

このとき硫酸濃度は7〜13%が好ましい。硫酸濃度が7%未満であると凝固浴中で糸条が凝固する速度が非常に遅くなるため所望の丸形もしくは扁平断面を得ることが困難となるので好ましくない。一方、硫酸濃度が13%を超えると繊維表面に付着した硫酸が脱酸されにくく焼成工程で糸切れが多発する他、凝固浴中で糸条が凝固する速度が非常に速くなり、この場合も断面形状のコントロールが困難となるので好ましくない。   At this time, the sulfuric acid concentration is preferably 7 to 13%. If the sulfuric acid concentration is less than 7%, the rate at which the yarn solidifies in the coagulation bath becomes very slow, which makes it difficult to obtain the desired round shape or flat cross section. On the other hand, if the sulfuric acid concentration exceeds 13%, the sulfuric acid attached to the fiber surface is not easily deoxidized, and yarn breakage occurs frequently in the firing process, and the rate at which the yarn solidifies in the coagulation bath becomes very fast. This is not preferable because it is difficult to control the cross-sectional shape.

硫酸ソーダ濃度は7〜15%に調整することが好ましい。硫酸ソーダはセルロースの急激な凝固を抑制する。硫酸ソーダ濃度が7%未満の場合、凝固浴中で糸条が凝固する速度が非常に速くなり、断面形状のコントロールが困難となるので好ましくない。一方、硫酸ソーダ濃度が15%を超える場合、凝固浴中で糸条が凝固する速度が非常に遅くなるため所望の断面形状を得ることが困難となり好ましくない。すなわち、本発明ではマトリックス法を用いて上記した硫酸濃度及び硫酸ソーダ濃度の両方を特定の範囲内に調整することで均一なPTFE繊維を製造することができたのである。   It is preferable to adjust the sodium sulfate concentration to 7 to 15%. Sodium sulfate suppresses rapid coagulation of cellulose. When the sodium sulfate concentration is less than 7%, the rate at which the yarn solidifies in the coagulation bath becomes very fast, and it becomes difficult to control the cross-sectional shape, which is not preferable. On the other hand, when the concentration of sodium sulfate exceeds 15%, the rate at which the yarn solidifies in the coagulation bath becomes very slow, which makes it difficult to obtain a desired cross-sectional shape, which is not preferable. That is, in the present invention, uniform PTFE fibers could be produced by adjusting both the sulfuric acid concentration and the sodium sulfate concentration within a specific range using the matrix method.

半焼成には接触タイプの焼成ローラまたは非接触タイプの焼成ヒーターを用いることができるが、好ましくは、接触タイプの焼成ローラを用いる。精練浴もしくはアルカリ浴から導かれた未焼成糸をそのままもしくはニップローラなどで絞った後、焼成ローラ間で1〜5%のリラックスを与えながら80以上320℃未満の温度の半焼成工程を行うことが必要である。80以上320℃未満の温度に保った接触タイプの半焼成工程のローラに導かれた未焼成糸はローラ上で急速に収縮し張力を増す。リラックス率が1%未満であれば張力が高くなりすぎて丸形もしくは扁平の断面形状を均一に保つことが困難となり、また、特に3.3dtex以下の細繊度糸を製造する場合には収縮による糸切れが多発してしまう。5%を超えるとリラックス率が高すぎて糸が弛み工程通過性に問題が生じてしまう。但し、1〜5%のリラックスは、半焼成に入った直後の焼成ローラ間に1回だけではなく半焼成工程のローラ間や焼成工程のローラ間においても行うことができる。半焼成工程は次いで行う焼成工程に入る前になくてはならない工程である。半焼成工程のローラ温度が80℃より低い場合は、次いで行う焼成工程で一気に繊維に熱がかかるため繊維断面が変形もしくは単糸間での融着が発生する。一方、320℃より高い場合は半焼成段階で一気に繊維に熱がかかるため繊維断面が変形もしくは単糸間での融着が発生しやすい。従って、半焼成工程のローラは80以上320℃未満の温度の範囲に保つことが必要である。   For the half firing, a contact type firing roller or a non-contact type firing heater can be used, but a contact type firing roller is preferably used. After squeezing the unfired yarn derived from the scouring bath or the alkali bath as it is or with a nip roller, a semi-baking step at a temperature of 80 to less than 320 ° C. is performed while relaxing 1 to 5% between the firing rollers. is necessary. The unfired yarn guided to the roller in the contact-type semi-baking process maintained at a temperature of 80 to 320 ° C. rapidly shrinks on the roller and increases the tension. If the relaxation rate is less than 1%, the tension becomes too high and it becomes difficult to keep the round or flat cross-sectional shape uniform. In particular, when producing fine yarns of 3.3 dtex or less, it is caused by shrinkage. Many thread breaks occur. If it exceeds 5%, the relaxation rate is too high, and the yarn loosens, causing a problem in the processability. However, the relaxation of 1 to 5% can be performed not only once between the firing rollers immediately after entering the semi-baking, but also between the rollers in the semi-baking process or between the rollers in the baking process. The semi-baking process is a process that must be performed before entering the subsequent baking process. When the roller temperature in the semi-baking process is lower than 80 ° C., the fiber is heated at a stretch in the subsequent baking process, so that the fiber cross section is deformed or fusion between single yarns occurs. On the other hand, when the temperature is higher than 320 ° C., the fiber is heated at a stretch in the semi-firing stage, so that the fiber cross section is easily deformed or fusion between single yarns easily occurs. Therefore, it is necessary to keep the roller in the semi-baking step in a temperature range of 80 to 320 ° C.

この時、各ローラ温度は単独で変更出来、上記範囲内で有れば特に限定無く設定できる。焼成ローラ数により半焼成工程のローラ温度は異なる。半焼成工程のローラ温度は、好ましくは150以上320℃未満、より好ましくは250以上320℃未満である。   At this time, each roller temperature can be changed independently, and can be set without any limitation as long as it is within the above range. The roller temperature in the semi-baking process varies depending on the number of baking rollers. The roller temperature in the semi-baking step is preferably 150 or more and less than 320 ° C, more preferably 250 or more and less than 320 ° C.

次いで、半焼成された糸は320〜380℃の温度で焼成される。この段階でセルロースの大部分は燃焼飛散し、セルロース中のPTFE粒子は繊維状に熱融着してPTFE未延伸糸が得られる。焼成温度が320℃より低いと繊維内のPTFE粒子同士の融着が不十分で、焼成後の延伸時に糸切れが頻発する他、繊維強度も低くなり好ましくない。一方、焼成温度が380℃より高いと熱により繊維断面形状が変形し所望の均一な断面形状を得ることが困難となってしまう。また、単糸間の融着も生じ製品の開繊性に悪影響を与える結果となるので好ましくない。また、焼成時、各ローラ温度は単独で変更出来、上記範囲内で有れば特に限定無く設定できる。   The semi-fired yarn is then fired at a temperature of 320-380 ° C. At this stage, most of the cellulose is burned and scattered, and the PTFE particles in the cellulose are thermally fused in a fibrous form to obtain an unstretched PTFE yarn. When the firing temperature is lower than 320 ° C., the PTFE particles in the fiber are not sufficiently fused, and yarn breakage frequently occurs during stretching after firing, and the fiber strength is also lowered. On the other hand, if the firing temperature is higher than 380 ° C., the fiber cross-sectional shape is deformed by heat, and it becomes difficult to obtain a desired uniform cross-sectional shape. Further, it is not preferable because fusion between single yarns also occurs, resulting in an adverse effect on the openability of the product. Moreover, at the time of baking, each roller temperature can be changed independently, and if it exists in the said range, it can set without limitation.

次いでPTFE未延伸糸は、通常用いられる公知の延伸方法で一旦巻き取るか、もしくはそのまま300〜400℃の温度で熱延伸されてPTFE延伸糸が得られる。   Next, the PTFE undrawn yarn is wound once by a commonly used known drawing method, or directly heat-drawn at a temperature of 300 to 400 ° C. to obtain a PTFE drawn yarn.

また、焼成の際に非接触タイプの焼成ヒーターを用い上記と同様にし製造することもできる。   Further, it can be produced in the same manner as described above using a non-contact type firing heater during firing.

精錬された後、半焼成、焼成工程を行う前に0.08〜0.16%のアルカリ濃度でアルカリによる洗浄工程を行うことが好ましい。かかるアルカリ洗浄浴には、アルカリ金属またはアルカリ土類金属の水酸化物、炭酸塩、重炭酸塩から選ばれた化合物の水溶液を用いるが、一般にはアルカリ金属の水溶液、中でも苛性ソーダ水溶液が好適に用いられる。該化合物の濃度は0.08〜0.16wt%が好ましい。一般に、次工程の焼成温度範囲にもよるが、PTFE繊維は焼成工程に入る際、繊維表面に酸成分が残存していると焼成工程での糸切れが頻発する。従来の3.3dtexを越える太繊度PTFE繊維であれば、精錬工程のみでもその精錬時間を長く考慮すれば洗浄は十分である。しかしながら、本発明でいう3.3dtex以下の細繊度PTFE繊維を製造する場合には、その細繊度糸表面の広い表面積ゆえ、表面の酸成分をアルカリで中和および洗浄することが好ましい。アルカリによる洗浄は脱酸による糸切れ抑制の他に焼成具合つまり色目やフィブリル化しやすさにも影響を与える。本発明の半焼成及び焼成温度の範囲内であれば、アルカリ浴の濃度が0.08〜0.16%が好ましい。アルカリ浴の濃度が0.08wt%未満であると焼成時にセルロース分が分解しにくく、その結果、焼成後の繊維に分解しきれないセルロース分が多く残存し、その後の延伸がしにくくなり、延伸工程で糸切れが頻発する傾向となる。一方、アルカリ浴の濃度が0.16wt%を超えるとアルカリ洗浄時にセルロースが溶けだし、アルカリ浴中やガイドにカスが溜まりやすくなる。また半焼成・焼成工程に入る際の未焼成糸強度が弱くなり、工程通過性トラブルを発生しやすくなるので好ましくない。また、焼成時繊維内部のPTFE粒子同士の融着が強固となり、フィブリル化しにくくなるので好ましくない。より好ましいアルカリ濃度は、0.10〜0.14wt%である。   After the refining, it is preferable to perform a washing step with an alkali at an alkali concentration of 0.08 to 0.16% before performing the semi-baking and baking steps. In such an alkali cleaning bath, an aqueous solution of a compound selected from alkali metal or alkaline earth metal hydroxides, carbonates and bicarbonates is used, but generally an aqueous alkali metal solution, particularly an aqueous caustic soda solution is preferably used. It is done. The concentration of the compound is preferably 0.08 to 0.16 wt%. Generally, although depending on the firing temperature range of the next step, when PTFE fiber enters the firing step, yarn breakage frequently occurs in the firing step if an acid component remains on the fiber surface. If the PTFE fiber has a fineness exceeding 3.3 dtex, the cleaning is sufficient even if only the refining process takes into account the refining time. However, when producing a PTFE fiber having a fineness of 3.3 dtex or less as referred to in the present invention, the surface acid component is preferably neutralized and washed with an alkali because of the large surface area of the fineness yarn surface. Washing with alkali affects not only the yarn breakage due to deoxidation, but also the degree of firing, that is, the color and fibrillation. If it is in the range of the semi-baking and baking temperature of this invention, the density | concentration of an alkaline bath is preferable 0.08 to 0.16%. When the concentration of the alkaline bath is less than 0.08 wt%, the cellulose content is difficult to decompose during firing, and as a result, a large amount of cellulose remains that cannot be decomposed in the fiber after firing, making subsequent stretching difficult and stretching. Yarn breakage tends to occur frequently in the process. On the other hand, when the concentration of the alkaline bath exceeds 0.16 wt%, the cellulose starts to dissolve during alkali cleaning, and the residue tends to accumulate in the alkaline bath or in the guide. Further, the strength of the unfired yarn at the time of entering the semi-firing / firing process becomes weak, and troubles in passing through the process are likely to occur, which is not preferable. Further, the fusion of the PTFE particles inside the fibers during firing becomes strong and is difficult to fibrillate. A more preferable alkali concentration is 0.10 to 0.14 wt%.

更にアルカリ浴の温度は、20℃以下が好ましい。アルカリ浴の温度が20℃を超えた場合もアルカリ濃度が高すぎる場合と同様にアルカリ洗浄時にセルロースが溶けだし、アルカリ浴中やガイドにカスが溜まりやすくなる他、半焼成・焼成工程に入る際の未焼成糸強度が弱くなり、工程通過性トラブルを発生しやすくなるので好ましくない。アルカリ浴の温度は、好ましくは15℃以下である。   Furthermore, the temperature of the alkaline bath is preferably 20 ° C. or less. When the temperature of the alkaline bath exceeds 20 ° C., the cellulose begins to dissolve during alkali washing, as in the case where the alkali concentration is too high, and the residue tends to accumulate in the alkaline bath and the guide. This is not preferable because the unfired yarn strength becomes weak and troubles in passing through the process easily occur. The temperature of the alkaline bath is preferably 15 ° C. or lower.

本発明に係るPTFE繊維は繊度が3.3dtex以下である。ダスト捕集効率を向上させる目的では表面積を上げるため細繊度化させることが有効である。しかし、一方で通気性を向上させる目的では太繊度化も要望される。この場合、本発明の細繊度PTFE繊維を他の太繊度繊維と混合して使用することができる。そうすることで通気性が高いレベルを保ったまま、ダスト捕集性能も高いフェルトが得られる。本発明の細繊度PTFE繊維は好ましくは2.2dtex以下であり、この範囲内においては、これまでのダスト捕集性能を遙かに凌ぐフェルトが得られる。   The PTFE fiber according to the present invention has a fineness of 3.3 dtex or less. In order to improve dust collection efficiency, it is effective to reduce the fineness in order to increase the surface area. However, increasing the fineness is also required for the purpose of improving air permeability. In this case, the fineness PTFE fiber of the present invention can be used by mixing with other thickness fiber. By doing so, it is possible to obtain a felt having a high dust collection performance while maintaining a high level of air permeability. The fineness PTFE fiber of the present invention is preferably 2.2 dtex or less. Within this range, a felt far exceeding the conventional dust collection performance can be obtained.

次に、本発明のPTFE異形断面繊維の繊度ばらつきは該繊維の繊度の10%以下であることが好ましい。前述した通り、スプリット剥離法やペースト押出法で得られる繊維の断面はランダムでその繊度も不均一である。従って、その繊度ばらつきも非常に大きい。そのため、ダスト捕集性能は良好であるが、その一方フェルト加工時にネップなどが生成されやすく加工が困難という欠点があった。本発明で細繊度化とともに繊度ばらつきを抑えた丸形もしくは扁平断面のPTFE繊維を発明したことでこれらの両立ができるようになったのである。繊度ばらつきが該繊維の繊度の10%を超えることは、断面形状および繊度が不均一であることを意味しており、安定した加工を行うことが困難となり好ましくない。   Next, it is preferable that the variation in fineness of the PTFE modified cross-section fiber of the present invention is 10% or less of the fineness of the fiber. As described above, the cross section of the fiber obtained by the split peeling method or paste extrusion method is random and the fineness is not uniform. Therefore, the fineness variation is very large. For this reason, the dust collecting performance is good, but on the other hand, there is a drawback that a nep or the like is easily generated during the felt processing, and the processing is difficult. Inventing a round or flat cross-section PTFE fiber with reduced fineness and reduced fineness in the present invention makes it possible to achieve both of these. When the fineness variation exceeds 10% of the fineness of the fiber, it means that the cross-sectional shape and the fineness are not uniform, and it is difficult to perform stable processing, which is not preferable.

一方、フェルト加工時に本発明で得られる繊度の異なる繊度ばらつきを10%以下に抑えたPTFE断面繊維同士、もしくは繊度の異なる繊度ばらつきを10%以下に抑えたPTFE繊維と丸断面繊維やスプリット剥離法やペースト押出法で得られる繊維は適正な混合割合で用いても工程通過性に問題なく実施できる。   On the other hand, PTFE cross-section fibers in which the fineness variation with different fineness obtained in the present invention during felt processing is suppressed to 10% or less, or PTFE fibers and round cross-section fibers in which the fineness variation with different fineness is suppressed to 10% or less, or a split peeling method. Even if the fiber obtained by the paste extrusion method is used in an appropriate mixing ratio, it can be carried out without any problem in process passability.

本発明の繊維断面は丸形もしくは扁平の繊維断面を有するPTFE繊維である。   The fiber cross section of the present invention is a PTFE fiber having a round or flat fiber cross section.

更に本発明のPTFE繊維をカットして短繊維として使用する際には、繊維長は、30〜100mm程度であればよいが、特に限定されない。   Furthermore, when the PTFE fiber of the present invention is cut and used as a short fiber, the fiber length may be about 30 to 100 mm, but is not particularly limited.

本発明のPTFE繊維の単糸強度は0.7cN/dtex以上、単糸伸度は50%以下であることが好ましい。単糸強度が0.7cN/dtex未満、単糸伸度が50%を越える繊維を後加工する場合、単繊維が延伸され、工程通過性不良となるので好ましくない。
また、本発明の短繊維の300℃×30分における乾熱収縮率は30%以下であることが好ましい。実際フェルトなどを作製して使用する場合、その素材のもつ耐熱性ゆえ、高温度下で使用される用途が多く収縮が高すぎるフェルトが収縮し、目詰まりも起こしやすく好ましくない。乾熱収縮率は、より好ましくは20%以下である。
The single yarn strength of the PTFE fiber of the present invention is preferably 0.7 cN / dtex or more, and the single yarn elongation is preferably 50% or less. When a fiber having a single yarn strength of less than 0.7 cN / dtex and a single yarn elongation of more than 50% is post-processed, the single fiber is stretched, resulting in poor processability.
Moreover, it is preferable that the dry heat shrinkage rate in 300 degreeC * 30 minutes of the short fiber of this invention is 30% or less. When a felt is actually produced and used, because of the heat resistance of the material, the felt that is used in a high temperature and has a shrinkage that is too high shrinks and is likely to be clogged. The dry heat shrinkage is more preferably 20% or less.

本発明でいう少なくとも一部に本発明のPTFE繊維を用いた布帛とは、その形態は織編物、不織布、フェルトなど特に限定されない。また、該布帛は本発明のPTFE繊維とともにガラス繊維やアラミド、ポリフェニレンサルファイド、ポリイミド、ポリパラフェニレンベンゾオキサゾールなどと混合して作製することができる。しかし、アラミドは分解温度が500℃以上と優れているが、耐酸性が低い弱点があり、ポリフェニレンサルファイドは耐薬品性に優れるものの、融点が285℃と耐熱性がやや低い。ポリイミドの場合耐アルカリ性にやや問題があり、ポリフェニレンベンゾオキサゾールは、高強度ではあるが、市場価格が非常に高価である。ガラス繊維は分解点が700℃以上と耐熱性は問題ないが、耐アルカリ性にやや問題がある。これに対してフッ素樹脂系繊維、中でもPTFEは特定の過フッ化有機液体に299℃以上で溶けることと、溶融アルカリ金属にわずかに侵される以外は、非常に優れた耐薬品性を示し、また耐熱性も融点が327℃と高温であることから総合的に見てフッ素樹脂系繊維が最もバランスよく優れた性能を発揮する。そのため、最もフィルター用途に好適である。その混合比率としては本発明のPTFE繊維を20〜100%、好ましくは40〜100%の割合で混繊することが好ましい。本発明のPTFE繊維はそのまま布帛として使用することもできるが、以下で言うフィブリル化した布帛として使用するとより効果的である。   The form using the PTFE fiber of the present invention as at least a part of the present invention is not particularly limited in its form such as woven / knitted fabric, non-woven fabric and felt. The fabric can be prepared by mixing glass fiber, aramid, polyphenylene sulfide, polyimide, polyparaphenylenebenzoxazole and the like together with the PTFE fiber of the present invention. However, although aramid has an excellent decomposition temperature of 500 ° C. or higher, it has a weak point of low acid resistance. Polyphenylene sulfide has excellent chemical resistance, but its melting point is 285 ° C., which is slightly low in heat resistance. In the case of polyimide, there is a slight problem in alkali resistance, and polyphenylenebenzoxazole has high strength, but the market price is very expensive. Glass fiber has a decomposition point of 700 ° C. or higher and no heat resistance, but has a slight problem with alkali resistance. In contrast, fluororesin fibers, especially PTFE, exhibit excellent chemical resistance except that they melt into a specific perfluorinated organic liquid at 299 ° C or higher and are slightly attacked by molten alkali metal. As for heat resistance, since the melting point is as high as 327 ° C., the fluororesin fiber exhibits the most balanced and excellent performance as a whole. Therefore, it is most suitable for filter applications. As the mixing ratio, it is preferable to mix the PTFE fiber of the present invention at a ratio of 20 to 100%, preferably 40 to 100%. Although the PTFE fiber of the present invention can be used as a fabric as it is, it is more effective when used as a fibrillated fabric as described below.

本発明でいうフィブリル化を有する布帛とは、フィブリル化したPTFE繊維が布帛表面の総面積の50%以上を占めることが好ましい。総面積の50%未満しか占有しない場合は、0.5μm以下のダストの捕集効率が低い布帛しか得ることができないからである。   The fabric having fibrillation referred to in the present invention preferably has fibrillated PTFE fibers occupying 50% or more of the total area of the fabric surface. This is because when less than 50% of the total area is occupied, only a fabric having a low dust collection efficiency of 0.5 μm or less can be obtained.

次に、かかる布帛の製造方法について説明する。すなわち、かかるフィブリル化したPTFE繊維からなる布帛は、フィブリル化していないPTFE繊維から構成される布帛の表面に、物理的衝撃を加えることで、該表面にフィブリル化したPTFE繊維を生成させる手段を用いて製造するものである。   Next, the manufacturing method of this fabric is demonstrated. That is, the fabric made of such fibrillated PTFE fibers uses a means for generating fibrillated PTFE fibers on the surface of the fabric made of non-fibrillated PTFE fibers by applying a physical impact. Are manufactured.

本発明の布帛では、表面に最小繊度が1.1dtex以下、更に0.1dtex以下であるフィブリル化したPTFE繊維があり、表面から内部に向かって繊度の大きいPTFE繊維の割合が漸次に増大する布帛が好ましい。なぜなら布帛の厚み方向で全体にわたってフィブリル化したPTFE繊維からなる布帛は、構成繊維が全て細く分割してしまったため、布帛の強度が低下してしまい好ましくない。また、布帛表面でフィブリル化したPTFE繊維と共に、布帛内部にフィブリル化せずに存在する異形断面を保ったPTFE繊維がダストの捕集効率を向上させる。ここでいうフィブリル化していないPTFE繊維からなる布帛は、PTFE短繊維からなるウェッブをニードルパンチで一体化したフェルトであれば、問題なく用いることができる。またここでいうフェルトにおいては、PTFE繊維の短繊維からなるウェッブと、耐熱性繊維のマルチフィラメントやモノフィラメントからなる織物からなる基布を積層したものでも良く、あるいはまた、フッ素樹脂系繊維(4フッ化エチレン−6フッ化プロピレン共重合体(FEP)、4フッ化エチレン− パーフロロアルコキシ基共重合体(PFA) または4フッ化エチレン− オレフィン共重合体(ETFE)など)からなる織物や編み物単体でも問題なく用いることができる。さらにまた、フィブリル化していないPTFE繊維からなる布帛は、PTFE繊維からなるウェッブ単体でも良く、あるいはまた、このウェッブをカレンダーした布帛や、樹脂を付着して硬化したレジンボンド不織布でも問題なく用いることができる。   In the fabric of the present invention, there is a fibrillated PTFE fiber having a minimum fineness of 1.1 dtex or less, and further 0.1 dtex or less on the surface, and the proportion of PTFE fibers having a high fineness gradually increases from the surface toward the inside. Is preferred. This is because a cloth made of PTFE fibers fibrillated in the thickness direction of the cloth is not preferable because all the constituent fibers are finely divided, and the strength of the cloth is lowered. Moreover, the PTFE fiber which maintained the irregular cross section which exists in the inside of a fabric without fibrillation with the PTFE fiber fibrillated on the fabric surface improves dust collection efficiency. The fabric made of non-fibrillated PTFE fibers can be used without any problem as long as it is a felt in which a web made of PTFE short fibers is integrated with a needle punch. The felt herein may be a laminate of a web made of short PTFE fibers and a base fabric made of a woven fabric made of heat-resistant multifilaments or monofilaments, or may be made of fluororesin fibers (4 fibers). Woven fabrics and knitted fabrics made of fluorinated ethylene-6 fluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxy group copolymer (PFA) or tetrafluoroethylene-olefin copolymer (ETFE), etc. But it can be used without problems. Further, the fabric made of non-fibrillated PTFE fiber may be a single web made of PTFE fiber, or may be used without any problem even with a fabric calendered with this web or a resin bonded nonwoven fabric cured by attaching a resin. it can.

本発明の物理的衝撃は、高圧ジェット水流処理であることが好ましい。なぜなら高圧ジェット水流処理をすることで、例えばニードルパンチなどによって発生する針穴や、繊維の断裂が発生するのを最小限に抑えて、物理的衝撃を与えることができるためである。   The physical impact of the present invention is preferably high pressure jet water flow treatment. This is because high-pressure jet water flow treatment can provide a physical impact while minimizing the occurrence of needle holes or fiber breaks caused by, for example, needle punching.

ここでいう高圧ジェット水流処理は3MPa.以上の処理圧が好ましい。丸断面のフッ素繊維と比べ、本発明で得られる異形繊維を用いることで処理圧を3MPa.まで低く設定してもフィブリルの発現が可能となり、繊維へ与えるダメージを極力抑えることが可能である。一方、処理圧が3MPa.未満であると繊維がフィブリル化せず、0.5μm以下のような微少ダストの捕集効率が低い布帛しか得られないため、好ましくない。   The high-pressure jet water flow treatment here is 3 MPa. The above processing pressure is preferable. Compared with the fluorine fiber having a round cross section, the processing pressure is 3 MPa. Even if set as low as possible, fibrils can be expressed, and damage to the fibers can be suppressed as much as possible. On the other hand, the treatment pressure is 3 MPa. If it is less than the range, the fiber is not fibrillated, and only a fabric having a low dust collection efficiency of 0.5 μm or less can be obtained.

本発明で得られる布帛はフィルター用材料または微粒子封止用材料用途に好適に用いることが出来る。本発明の布帛によれば、飛灰や粉塵を捕集するフィルターのみならず、さらには、液体用の濾過フィルターでも問題なく用いることができ、更には微粒子封止材料として、例えばプリンターのトナー封止材料などとして使用することができるが、これらの用途に限定されるものではない。   The fabric obtained by the present invention can be suitably used for filter materials or fine particle sealing materials. According to the fabric of the present invention, not only a filter that collects fly ash and dust, but also a filtration filter for liquid can be used without any problem. Further, as a fine particle sealing material, for example, a toner seal of a printer. Although it can be used as a stopping material, it is not limited to these uses.

以下、本発明について実施例を挙げて具体的に説明するが、本発明はこれらに限定されるものではない。なお、布帛の各物性の測定方法は以下の通りである。   EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these. In addition, the measuring method of each physical property of a fabric is as follows.

[繊度ばらつき]
フィブリル化させる前のPTFE延伸糸からサンプルをランダムに抜き取り下記の通り包埋法により断面写真を撮影する。その上でそれぞれの断面写真を切り取り重量を測定することで断面積を求め、本発明のPTFE繊維は比重2.30g/cmを用いて繊度を計算した。ランダムに30本測定し、平均値を算出する。その平均値と最小繊度、最大繊度の大きい方のばらつきの程度を測定した。
[Fineness variation]
A sample is randomly extracted from the PTFE drawn yarn before fibrillation, and a cross-sectional photograph is taken by the embedding method as described below. Then, each cross-sectional photograph was cut out and the weight was measured to determine the cross-sectional area, and the fineness of the PTFE fiber of the present invention was calculated using a specific gravity of 2.30 g / cm 3 . Thirty samples are randomly measured and the average value is calculated. The average value, the minimum fineness, and the degree of variation of the larger maximum fineness were measured.

<包埋法>
サンプル糸を成形枠にやや張力を加え粘着テープで固定する。200℃で加熱してパラフィンとステアリン酸の混合物を溶融させる。130℃になったらエチルセルロースを少量ずつ加え、攪拌しながら1時間保温して泡を抜く。100℃まで落とした後、成形枠に流し込む。冷却・固化させた後、適当な大きさのブロックに切り分ける。ミクロトームを用いて、ブロックから切片(厚さ7μm程度)を切り出し、スライドグラスの上に載せる。このとき、スライドグラス上にアルブメンを薄く塗り延ばしておく(アルブメンは卵の白身とグリセリン等量、防腐剤としてサリチル酸ソーダ1wt%添加したもの)。70℃に保った乾燥機に20分放置して熱処理を行い乾燥させた後、酢酸イソアミル浴に約1時間浸し、脱包埋を行ない、その後風乾する。スライドグラスの上に流動パラフィンを一滴つけ、空気が入らないようにカバーグラスを静かに載せ、顕微鏡を用いて写真を撮影する。
<Embedding method>
Apply some tension to the forming frame and fix it with adhesive tape. Heat at 200 ° C. to melt the mixture of paraffin and stearic acid. When the temperature reaches 130 ° C., ethyl cellulose is added little by little, and the mixture is kept warm for 1 hour with stirring to remove bubbles. After dropping to 100 ° C., it is poured into a forming frame. After cooling and solidifying, cut into blocks of appropriate size. Using a microtome, cut a section (thickness of about 7 μm) from the block and place it on a slide glass. At this time, thinly spread arbumen on a slide glass (albumen is an egg white and glycerin equivalent amount, and 1 wt% sodium salicylate is added as a preservative). It is left to stand in a dryer maintained at 70 ° C. for 20 minutes, heat-treated and dried, then immersed in an isoamyl acetate bath for about 1 hour, decapsulated, and then air-dried. Put a drop of liquid paraffin on the slide glass, place the cover glass gently so that air does not enter, and take a picture using a microscope.

[カード通過性]
室内温度30℃、相対湿度60%とし、カード機に2g/m〜10g/mの原綿を投入しつつ、ローラー通過時のシリンダーローラーの巻き付き、ネップの発生を観察し、以下のように評価した。
○ 良好
△ やや悪い
× 非常に悪い
[Card passability]
The room temperature was set to 30 ° C. and the relative humidity was set to 60%. While putting 2 g / m to 10 g / m of raw cotton into the card machine, the winding of the cylinder roller when passing through the roller and the occurrence of nep were observed and evaluated as follows. .
○ Good △ Somewhat bad × Very bad

[布帛表面の総面積に占めるフィブリル糸の割合(以下フィブリルの割合と記述)]
布帛の表面写真を撮影し、フィブリル糸の占める面積をよみとった。撮影倍率は50倍で、ビデオハイスコープを用いた。
[Proportion of fibril yarn in the total area of the fabric surface (hereinafter referred to as fibril proportion)]
A photograph of the surface of the fabric was taken and the area occupied by the fibril yarn was read. The photographing magnification was 50 times, and a video high scope was used.

[最小繊維径]
布帛の断面写真を電子顕微鏡で撮影し、最も繊維径の細い繊維を選択し、該繊維の繊維直径をよみとる。撮影倍率は1000倍とする。
[Minimum fiber diameter]
A cross-sectional photograph of the fabric is taken with an electron microscope, the fiber with the smallest fiber diameter is selected, and the fiber diameter of the fiber is read. The shooting magnification is 1000 times.

[ダスト捕集効率]
捕集効率は大気塵計数法により実施した。ダスト粒径は0.5μm以下、濾過風速は1.0m/分で、パーティクルカウンターを使用して、大気中のダストの捕集効率を測定したデータである。
[Dust collection efficiency]
The collection efficiency was carried out by the atmospheric dust counting method. The dust particle size is 0.5 μm or less, the filtration wind speed is 1.0 m / min, and the data is obtained by measuring the dust collection efficiency in the atmosphere using a particle counter.

(実施例1〜4)
ビスコース熟成度(塩点)8.0、セルロース濃度9.0%、アルカリ濃度6.2%のビスコース50重量%と濃度60%のPTFE水分散液50%を混合した後、10Torrの減圧下で脱泡して重合体濃度30%の成形用原液を得た。原液中のポリマーに対するPTFE樹脂含有量は87.0%であり、30℃における原液粘度は132ポイズであった。この原液を複数の吐出孔を有する成型用口金に導き、表1に示した断面形状、繊度になるように紡糸口金を次のように変更して凝固浴中に吐出した。
丸型断面形状繊維: 0.12mmφ×600ホール
扁平型断面形状繊維: 0.14mm(W)−0.08mm(L)×600ホール
(Examples 1-4)
Viscose maturity (salt point) 8.0, cellulose concentration 9.0%, alkali concentration 6.2% viscose 50% by weight and 60% concentration PTFE aqueous dispersion 50% mixed, then reduced pressure of 10 Torr Defoaming was performed below to obtain a forming stock solution having a polymer concentration of 30%. The PTFE resin content relative to the polymer in the stock solution was 87.0%, and the stock solution viscosity at 30 ° C. was 132 poise. This stock solution was introduced into a molding die having a plurality of ejection holes, and the spinning die was changed as follows so as to have the cross-sectional shape and fineness shown in Table 1, and was discharged into the coagulation bath.
Round cross-sectional shape fiber: 0.12 mmφ × 600 hole Flat cross-sectional shape fiber: 0.14 mm (W) −0.08 mm (L) × 600 hole

凝固浴は硫酸濃度10.0%、硫酸ソーダ濃度11.0%の混合水溶液であり、温度は10℃であった。次いで凝固した未焼成糸を温度80℃の温水で洗浄した後、濃度0.12%の苛性ソーダ水溶液を入れたアルカリ浴中に導いて精練し、酸成分を完全に除去した。その後、アルカリ浴から導かれた未焼成糸をニップローラで絞った後、4%のリラックスを与えながら280℃の温度で半焼成を行ない、次いで350℃に保った焼成ローラを用いて焼成を行い30m/分の速度で引き取り、未延伸糸を得た。次いで未延伸糸を350℃の温度で熱延伸し、表1に示す断面形状のPTFE延伸糸を得た。この紡糸、延伸工程において工程通過性は良好で1錘当たりの糸切れ回数は約12時間当たり1回の割合であった。   The coagulation bath was a mixed aqueous solution having a sulfuric acid concentration of 10.0% and a sodium sulfate concentration of 11.0%, and the temperature was 10 ° C. Next, the solidified unfired yarn was washed with warm water having a temperature of 80 ° C., and then introduced into an alkaline bath containing an aqueous caustic soda solution having a concentration of 0.12%, followed by scouring to completely remove the acid component. Thereafter, the unfired yarn led from the alkaline bath is squeezed with a nip roller, then subjected to half-baking at a temperature of 280 ° C. while giving a relaxation of 4%, and then baked using a baking roller kept at 350 ° C. An undrawn yarn was obtained by taking up at a speed of / min. Next, the undrawn yarn was heat-drawn at a temperature of 350 ° C. to obtain a PTFE drawn yarn having a cross-sectional shape shown in Table 1. In this spinning and drawing process, the process passability was good, and the number of yarn breaks per spindle was about once every 12 hours.

得られたPTFE延伸糸を合糸し、捲縮を掛けカットしてPTFEステープルを得た。該ステープルをカーディング処理してウェッブを得た。しかる後にPTFEマルチフィラメントよりなる織物(東レ・ファインケミカル製TOYOFLON#4300)の表裏両側に上記のウェッブを積層して、350本/cm2でニードルパンチ処理して一体化し、フェルトを得た(実施例3,4)。このフェルトの表面と裏面から3回ずつ処理水圧15MPa.、送り速度5m/minでウォータージェットパンチ処理し、表面のフィブリル化した布帛を得た(実施例1,2)。該繊維の繊度、繊度ばらつき、カード通過性、該布帛のフィブリルの割合、最小繊維径、捕集効率を測定した結果を表1に示す。 The obtained PTFE drawn yarns were combined, crimped and cut to obtain PTFE staples. The staple was carded to obtain a web. Thereafter, the above web was laminated on both the front and back sides of a woven fabric made of PTFE multifilament (TOYOFLON # 4300 manufactured by Toray Fine Chemical Co., Ltd.) and integrated by needle punching treatment at 350 pieces / cm 2 to obtain a felt (Example) 3, 4). The treatment water pressure is 15 MPa. 3 times from the front and back surfaces of the felt. Then, a water jet punching process was performed at a feeding speed of 5 m / min to obtain a fibrillated fabric (Examples 1 and 2). Table 1 shows the results of measurement of the fineness, fineness variation, card passing property, fibril ratio, minimum fiber diameter, and collection efficiency of the fiber.

(比較例1)
PTFEステープルファイバー(東レ・ファインケミカル社製“TOYOFLON“7.4dtex×70mm;丸断面)を用い実施例1と同様にしてフィブリル化した布帛を得た。実施例1,2と比較例1を比べると、本発明で得られる布帛は捕集効率が高いことが分かる。
(Comparative Example 1)
A fibrillated fabric was obtained in the same manner as in Example 1 using PTFE staple fiber (“TOYOFLON” 7.4 dtex × 70 mm; round cross section manufactured by Toray Fine Chemical Co., Ltd.). When Examples 1 and 2 are compared with Comparative Example 1, it can be seen that the fabric obtained in the present invention has high collection efficiency.

(比較例2)
フィブリル化を行わない点以外は比較例1と同様にして、フィブリル化していないフェルト布帛を得た。布帛のフィブリルの割合、最小繊維径、捕集効率を測定した。結果を表1に示す。フィブリル化していない布帛である実施例3,4と比較例2を比べると、本発明のPTFE繊維を用いた実施例3,4の方がダスト捕集効率は遙かに優れていた。
(Comparative Example 2)
A non-fibrillated felt fabric was obtained in the same manner as in Comparative Example 1 except that fibrillation was not performed. The fibril ratio, minimum fiber diameter, and collection efficiency of the fabric were measured. The results are shown in Table 1. When Examples 3 and 4 which are non-fibrillated fabrics were compared with Comparative Example 2, Examples 3 and 4 using the PTFE fibers of the present invention were far superior in dust collection efficiency.

Figure 2006207097
Figure 2006207097

(比較例3)
実施例1で得たPTFE水分散液原液を用い、この原液を複数の丸孔を有する成型用口金に導き、延伸糸の繊度が2.2dtexになるように凝固浴中に吐出した。凝固浴は硫酸濃度7%、硫酸ソーダ濃度20.0%の混合水溶液であり、温度は23℃であった。次いで凝固した未焼成糸を温度80℃の温水で洗浄した後、濃度0.05mol/l(0.2%)の苛性ソーダ水溶液を入れたアルカリ浴中に導いて精練し、酸成分を完全に除去した。その後、アルカリ浴から導かれた未焼成糸をニップローラで絞った後、本発明で言うリラックス半焼成を行うことなくそのまま380℃に加熱されたローラに接触させて焼成を行い30m/分の速度で引き取り、未延伸糸を得た。次いで未延伸糸を350℃の温度で熱延伸し、2.2dtexの丸形および扁平型の各断面形状のPTFE延伸糸を得た。
(Comparative Example 3)
Using the PTFE aqueous dispersion stock solution obtained in Example 1, this stock solution was introduced into a molding die having a plurality of round holes, and discharged into a coagulation bath so that the fineness of the drawn yarn was 2.2 dtex. The coagulation bath was a mixed aqueous solution having a sulfuric acid concentration of 7% and a sodium sulfate concentration of 20.0%, and the temperature was 23 ° C. Next, the coagulated unfired yarn is washed with warm water at a temperature of 80 ° C. and then introduced into an alkaline bath containing a caustic soda aqueous solution having a concentration of 0.05 mol / l (0.2%) and scoured to completely remove the acid component. did. Thereafter, the unfired yarn led from the alkaline bath is squeezed with a nip roller, and then fired by contacting it with a roller heated to 380 ° C. as it is without carrying out the relaxation semi-firing referred to in the present invention, at a speed of 30 m / min. The undrawn yarn was obtained by taking up. Subsequently, the undrawn yarn was heat-drawn at a temperature of 350 ° C. to obtain PTFE drawn yarns having a cross section of 2.2 dtex round and flat.

該条件では、硫酸ソーダ濃度が15%を超え、凝固浴中で糸条が凝固する速度が非常に遅くなったこと、またリラックス半焼成を行うことなくそのまま380℃に加熱されたローラに接触させて焼成を行った際の急激な熱収縮により工程通過性は不良であり、紡糸、延伸工程において糸切れが激しく1錘当たりの糸切れ回数は約10分当たり1回の割合であった。また、リラックス半焼成を経ず急激に熱焼成を実施したため、延伸後の延伸糸の単糸間融着が激しく、そのため繊維ばらつきも丸形が±18%、扁平形が±24%と非常に大きな値となった。   Under these conditions, the concentration of sodium sulfate exceeded 15%, the rate at which the yarn solidified in the coagulation bath became very slow, and it was brought into contact with a roller heated to 380 ° C. without relaxing and semi-firing. Due to the rapid thermal shrinkage during firing, the process passability was poor, and the yarn breakage was severe in the spinning and drawing process, and the number of yarn breakage per spindle was about once every 10 minutes. In addition, since the thermal firing was performed rapidly without relaxing and semi-firing, the stretched yarns after drawing were severely fused between the single yarns, and therefore the fiber variation was extremely ± 18% for round and ± 24% for flat. It was a big value.

これらの結果から明らかなように、本発明で得られる細繊度PTFE糸を用いると、より微小なダストの捕集性に優れた布帛を得ることができる。また、マトリックス紡糸法により製造される丸形、もしくは扁平の繊維断面を有する3.3dtex以下のPTFE繊維を製造するためには、本発明で言うPTFEの水分散液との混合液を特定の成分、濃度に調整された凝固浴に複数の口金孔から吐出し、紡糸を行う製造方法で、特に焼成を行う際、特定の弛緩率でリラックスを与えながら、特定温度で半焼成工程を経た後に特定温度で焼成を行うことが必要であることが分かる。   As is apparent from these results, when the fineness PTFE yarn obtained in the present invention is used, it is possible to obtain a fabric excellent in the ability to collect fine dust. In addition, in order to produce a PTFE fiber of 3.3 dtex or less having a round or flat fiber cross section produced by a matrix spinning method, a mixture of the PTFE aqueous dispersion referred to in the present invention is a specific component. , A manufacturing method in which spinning is performed through a plurality of die holes in a coagulation bath adjusted to a concentration, and spinning is performed, especially when firing is performed, and after a semi-baking step at a specific temperature while giving relaxation at a specific relaxation rate It can be seen that it is necessary to perform firing at temperature.

Claims (8)

マトリックスとしてのビスコースとポリテトラフルオロエチレンの水分散液との混合液を、硫酸濃度7〜13%、硫酸ソーダ濃度7〜15%を含有する凝固浴中に複数の口金孔から吐出し、紡糸、精練した後、焼成ローラ間で1〜5%のリラックスを与えながら80以上320℃未満の温度で半焼成した後、320〜380℃の温度で焼成を行ない、一旦巻き取るか、もしくはそのまま延伸して繊度が3.3dtex以下でかつ繊度ばらつきが10%以下である、丸形断面もしくは扁平断面のポリテトラフルオロエチレン繊維を製造することを特徴とするポリテトラフルオロエチレン繊維の製造方法。   A mixture of viscose as a matrix and an aqueous dispersion of polytetrafluoroethylene is discharged from a plurality of nozzle holes into a coagulation bath containing a sulfuric acid concentration of 7 to 13% and a sodium sulfate concentration of 7 to 15%, and spinning. After scouring, semi-baking at a temperature of 80 to less than 320 ° C. while giving a relaxation of 1 to 5% between the baking rollers, baking at a temperature of 320 to 380 ° C., and winding up once or stretching as it is A method for producing a polytetrafluoroethylene fiber having a round cross section or a flat cross section having a fineness of 3.3 dtex or less and a fineness variation of 10% or less. 接触タイプの焼成ローラを用いて半焼成することを特徴とする請求項1記載のポリテトラフルオロエチレン繊維の製造方法。   The method for producing a polytetrafluoroethylene fiber according to claim 1, wherein semi-firing is performed using a contact-type calcining roller. 半焼成および焼成の前にアルカリ濃度0.08〜0.16wt%のアルカリ水溶液による洗浄を行うことを特徴とする請求項1または2記載のポリテトラフルオロエチレン繊維の製造方法。   The method for producing polytetrafluoroethylene fibers according to claim 1 or 2, wherein washing with an alkaline aqueous solution having an alkali concentration of 0.08 to 0.16 wt% is performed before half-firing and firing. 請求項1〜3いずれか記載のポリテトラフルオロエチレン繊維の製造法にて得られるポリテトラフルオロエチレン繊維。   The polytetrafluoroethylene fiber obtained by the manufacturing method of the polytetrafluoroethylene fiber in any one of Claims 1-3. 請求項4記載のポリテトラフルオロエチレン繊維を少なくとも一部に用いた布帛。   A fabric using at least part of the polytetrafluoroethylene fiber according to claim 4. フィブリルを有することを特徴とする請求項5に記載の布帛   The fabric according to claim 5, comprising fibrils. 請求項5または6記載の布帛を用いてなるフィルター用材料。   A filter material comprising the fabric according to claim 5. 請求項5または6記載の布帛を用いてなる微粒子封止用材料。   A fine particle sealing material using the fabric according to claim 5.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008088581A (en) * 2006-09-29 2008-04-17 Toray Ind Inc Polytetrafluoroethylene fiber and method for producing the same
WO2009141899A1 (en) * 2008-05-21 2009-11-26 株式会社フジコー Felt material for air filter
RU2469133C1 (en) * 2008-12-19 2012-12-10 Гор Энтерпрайз Холдингс, Инк. Articles from fabric of ptfe and method of their manufacturing
RU2469132C1 (en) * 2008-12-19 2012-12-10 Гор Энтерпрайз Холдингс, Инк. Articles from fabric of ptfe and method of their manufacturing
CN110184661A (en) * 2019-07-02 2019-08-30 常州蓦晟非织造有限公司 A kind of preparation method and equipment of polytetrafluoroethylene (PTFE) brown fibre

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008088581A (en) * 2006-09-29 2008-04-17 Toray Ind Inc Polytetrafluoroethylene fiber and method for producing the same
WO2009141899A1 (en) * 2008-05-21 2009-11-26 株式会社フジコー Felt material for air filter
JPWO2009141899A1 (en) * 2008-05-21 2011-09-29 株式会社フジコー Felt material for air filter
RU2469133C1 (en) * 2008-12-19 2012-12-10 Гор Энтерпрайз Холдингс, Инк. Articles from fabric of ptfe and method of their manufacturing
RU2469132C1 (en) * 2008-12-19 2012-12-10 Гор Энтерпрайз Холдингс, Инк. Articles from fabric of ptfe and method of their manufacturing
CN110184661A (en) * 2019-07-02 2019-08-30 常州蓦晟非织造有限公司 A kind of preparation method and equipment of polytetrafluoroethylene (PTFE) brown fibre

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