JP4429501B2 - Molten liquid crystalline polyester nonwoven fabric and method for producing the same - Google Patents
Molten liquid crystalline polyester nonwoven fabric and method for producing the same Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は溶融異方性芳香族ポリエステル繊維からなり、防護材、土質改良材、振動材、研磨材、電気絶縁材料等に有効な不織布に関する。
【０００２】
【従来の技術】
有機繊維から不織布を製造する技術としては、湿式不織布及び乾式不織布が主流であるが、湿式不織布は、そのままでは強度がないため、フィブリル化した繊維や、バインダー繊維を混繊した後、絡合させ、熱処理や水流絡合処理等を施さなければならず、工程が複雑化し製造コストが上るばかりでなく例えば電気絶縁材料等に問題視される異物（金属・異種繊維）の混入の可能性が増大する。また乾式不織布は、地合が悪く精度を要求されるプリント配線基板用の基材には不向きとなる。
一方、溶融液晶ポリエステルを使用して、紡糸直結で不織布を作成するスパンボンド法等が特開平６―１２８８５７号公報で提案されており、溶融液晶ポリエステルのスパンボンド不織布を用い、カレンダー処理及び熱処理する方法が記載されている。しかしながら、スパンボンド法では紡糸後フィラメントを開繊するため繊維同士が交絡点で融着されず、バインダー成分が必要となるのである。溶融液晶ポリエステル単独であればカレンダー処理及び熱処理しても繊維交絡点のみ融着させることは不可能で、不織布自体が融着を起こしフィルム化してしまう。ポリマー融点前後の温度でカレンダー掛けして巻き取るとロール線圧により、ポリマーが軟化し不織布はズルズルと伸びてしまう。反対に引張しなければ収縮を起こし安定した形態に成らないのである。そのため融点以下の温度で熱処理することにより、フィラメント自体の結晶化が増し、不織布のタテ方向は強くなるがヨコ方向は繊維交絡点の融着がないために非常に弱いものである。一方向は強いが反対方向は非常に弱くなるといったバランスの悪いものとなり、利用範囲が少ないのである。
【０００３】
【発明が解決しょうとする課題】
本発明は、上記のような溶融液晶ポリエステルからなる不織布の強度面及び異物混入の課題を解決することを目的とするものである。
【０００４】
【課題を解決するための手段】
すなわち本発明は、平均繊維径が０．６〜２０μｍの繊維が６０％以上含まれる溶融液晶性ポリエステル繊維から構成され、タテ方向の裂断長が１．５Ｋｍ以上、３００℃１時間での面積収縮率が３％以下であることを特徴とするメルトブローン不織布であり、また本発明は、溶融液晶性ポリエステルを溶融紡出すると同時に、紡出物を高温高速流体で吹き飛ばし、捕集面上に集積してウエブを形成し、該ウエブにカレンダー加工及び加熱処理を施して不織布を製造するに際し、不織布の表面温度が９０℃以上で溶融液晶性ポリエステルの融点温度以下、線圧５０ｋｇ／ｃｍ以上２００ｋｇ／ｃｍ以下でカレンダーロール間に間隙（コッター）を設け、製品予定厚み前後の間隙にしてカレンダー加工を行ない、（溶融液晶性ポリエステルの融点温度−４０℃）以上、（融点温度＋２０℃）以下の温度で３時間以上加熱処理を行うことを特徴とする溶融液晶性ポリエステル繊維からなるメルトブローン不織布の製造方法である。
【０００５】
【発明の実施の形態】
本発明に言う溶融液晶性ポリエステルとは、芳香族ジオール、芳香族ジカルボン酸、芳香族ヒドロキシカルボン酸等より重合されて得られるポリマーであり、溶融相で光学的異方性（液晶性）を示すものからなる繊維である。このような特性はホットステージ上の試料を窒素雰囲気下で昇温し、その透過光を観察することにより容易に認定することができる。
【０００６】
本発明に用いられる溶融液晶性ポリエステルは、例えば、下記化１及び化２に示す反復構成単位の組合せからなるものである。
【０００７】
【化１】
特に好ましくは、下記化３に示す（Ａ）、（Ｂ）の反復構成単位からなる部分が６５モル％以上である芳香族ポリエステルであり、特に（Ｂ）の成分が４〜４５モル％である芳香族ポリエステルが好ましい。
【０００９】
【化３】
なお、ポリエステル中には、その強力が実質的に低下しない範囲で他のポリマー或いは添加剤等を含んでもよい。
【００１１】
次に本発明で言う溶融液晶ポリエステル繊維からなる不織布とは、メルトブローン不織布のことであり、ノズルから溶融液晶性ポリエステルを溶融紡出すると同時に、高温高圧のガスにより、溶融液晶性ポリエステルを細かい繊維状に吹き飛ばしサクションしている捕集面（例えば、金網）上に捕集して製造される不織布である。
【００１２】
しかしながら、従来の溶融液晶ポリエステルを用いたメルトブローン不織布は高融点ポリマーで、固化が早く、高粘度のためビス落ちし中間体としてしか使えず満足な不織布製品とすることが困難であり、好ましくは、融点が２８０℃以上、溶融粘度が２５Ｐａ・ｓ以下、特に好ましくは２０Ｐａ・ｓ（温度３２０℃・せん断速度１０００sec-1下）の溶融液晶性ポリエステルを用いことが好ましい。このようなポリエステルを用いてメルトブローンされた不織布は、地合良好で耐熱性・寸法安定性・低吸水性・樹脂含浸性を備えるものである。
【００１３】
メルトブローン法により捕集面上に集積される繊維の平均径はノズル径、吐出量、エアー速度より決まるが、本発明の場合、平均繊維径が０．６〜２０μｍであり、好ましくは１μｍ〜１５μｍ、特に１〜１０μｍの繊維が６０％以上含まれ、強度と柔軟性や通気性を備えているものである。なお、本発明において平均繊維径は、不織布を走査型電子顕微鏡で拡大撮影し、任意の１００本の繊維の径を測定した値の平均値を指すものである。
【００１４】
また集積された不織布は、薄くするほど目付斑ができやすく、タテ方向よりもヨコ方向に出やすい。この目付斑を表すのにＣＶ（％）値で表し、ＣＶ（％）値が３％以上になると薄いところが強度不足となり、工程通過性や製品物性に悪影響を及ぼし満足な製品にならない、好ましくは２％以下である。
【００１５】
次いで本発明では、メルトブローン後、オフライン又はオンラインのコンベアー上で不織布表面がポリマーのガラス転移点を超える９０℃以上になるようにロール温度を設定し、溶融液晶性ポリエステルの融点温度以下、線圧５０kg/cm以上２００kg/cm以下でカレンダー処理することが望ましい。
カレンダー処理は、オンラインでもオフライン方式でも良いがオンラインの方が好ましい。一般的に不織布を温度が９０℃未満でカレンダー処理した場合には、その温度が不織布を形成している溶融液晶性ポリエステルのガラス転移点に達しないので繊維が変形固着や埋め込みが無く強度が上がらない。そのため目的の厚みになったものが次第に元の厚さに復帰して要求される製品の厚さにはならない。
【００１６】
一方、カレンダーロール温度が溶融液晶性ポリエステルの融点を超えるとロールへ不織布が溶融接着して、ロール捲き付きが発生する。
【００１７】
得られる不織布の厚さをより均一にするためには、カレンダーロール間に間隙（コッター）を設け、製品予定厚み前後の間隙にしてカレンダー処理することが好ましい。
【００１８】
カレンダー処理時のロール線圧が５０kg/cm未満であると、ロールの押えが少なく、繊維交絡点の変形固着や埋め込みが無く不織布は暫くしてもとの厚さに戻ってしまい目的の厚みの不織布を形成することができない。また、次の熱処理するためには嵩高のままでは大きな熱処理機が必要となりコスト高になる。
【００１９】
一方、ロール線圧が２００kg/cmを超えて大きくなった場合には、絡みは多くなるが座屈を起こしたり、繊維交絡点が押しつぶされてしまい、不織布の形態が悪く工程通過性が悪くなる。従って、不織布表面温度が９０℃以上溶融液晶性ポリエステルの融点温度以下、線圧５０kg／cm以上２００kg／cm以下でカレンダー処理することが望ましい。
【００２０】
本発明においては、カレンダー処理後、不織布を高温気体中で(溶融液晶性ポリエステルの融点温度―４０℃)以上、(融点温度＋２０℃)以下の温度で３時間以上熱処理する。好ましくは３時間以上７２時間以下熱処理し、点融着されている繊維交絡点および繊維自体の配向を進めて不織布のタテ・ヨコ方向の強度を増大する。
【００２１】
（溶融液晶性ポリエステルの融点温度―４０℃）未満の温度で熱処理した場合には、熱処理により生ずる溶融液晶性ポリエステルの固相重合が進まず、熱処理に時間を掛けるだけで、不織布強度を向上させるこはできない。反対に(溶融液晶性ポリエステルの融点温度―４０℃)を超えて熱処理温度を高くすると、繊維交絡点及び繊維自体の配向が進み、不織布の強度が増す。熱処理温度は（溶融液晶性ポリエステルの融点温度―３０℃）以上で、さらに好ましくは（溶融液晶性ポリエステルの融点温度―２０℃）以上で行うのが好ましい。
【００２２】
一方、熱処理温度が（溶融液晶性ポリエステルの融点温度＋２０℃）を超えると溶融液晶性ポリエステルが軟化してきて繊維の溶融が始まり、繊維と繊維が接着してフイルム化する。そのため通気性や柔軟性が無くなったり、例えば後工程で樹脂含浸を行う場合に、その含浸性が悪くなり、含浸率が低くなるといった不都合が生じる。
【００２３】
加熱媒体として用いる気体は、窒素、酸素、アルゴン、炭酸ガス等混合気体及び空気等が用いられる。用いる気体は露点が−２０℃以下であることが好ましい。熱処理は目的により緊張下、無緊張下どちらでもよい。このようにして、カレンダー処理後、不織布を加熱気体中で（溶融液晶性ポリエステルの融点温度―４０℃）以上、（溶融液晶性ポリエステルの融点温度＋２０℃）以下の温度で熱処理して、メルトブローン後すでに繊維交点で点融着されているところの繊維交絡点及び繊維自体の配向を進めて不織布のタテ方向、ヨコ方向とも高強力にさせるのである。
【００２４】
熱処理された不織布は、３００℃×１時間後での面積収縮率３％以下、好ましくは２％以下の面積収縮率を示し、優れた寸法安定性と、融点３２５℃以上の高耐熱性と、タテ裂断長２．５Ｋｍ以上、ヨコ裂断長１．5Ｋｍ以上の優れた物性を持ったものである。これよりも劣る品質では後工程の通過性が不良となったり、精度を要求される産業資材には使用できない。
【００２５】
本発明では、湿式不織布を製造する場合に必須であるパルプ化、カット、抄紙等の工程を必要としないため、工程での不織布への異物（金属）の混入の懸念が少なくなり、例えば、電気絶縁材料等に使用することが可能である。またスパンボンド法では太デニールとなったり、バインダー接着または他のバインダー不織布の積層が必要になり、薄厚で精密を要する材料には不適であったが本発明により初めて溶融液晶ポリエステル１００％で持ってバインダーを使用しなくとも可能となったのである。
【００２６】
【実施例】
以下、本発明を実施例により具体的に説明するが本発明これらの記載事項に限定されるものではない。本実施例、比較例において記載されている測定数値は次の方法で行った。
【００２７】
[裂断長 ｋｍ ]
巾１５ｍｍ試料長４cmのＭＤ方向のＤＲＹの強力を測定し裂断長をもとめた。
【００２８】
[目付斑（ＣＶ）％]
連続に５ｃｍ角に切り取り重量を測定し目付斑としてＣＶであらわす。ここにＣＶ（％）＝σｎ／平均値×１００
【００２９】
[融点 ℃]
ＤＳＣ（例えばＭｅｔｔｌｅｒ社製ＴＡ3000）装置にサンプルを１０ｍｇとり、アルミ製パンへ封入後、窒素を５０cc／min流し、昇温速度２０℃／minで測定、吸熱ピーク温度の頂点を測定する。1stランで明確なピーク温度が現れないときは５０℃／minの昇温で、予想される融点よりも５０℃高い温度で3分間程度完全に溶融した後８０℃／min５０度まで冷却し、しかる後２０℃／minの昇温速度で測定する。
【００３０】
[溶融粘度 Ｐａ・ｓ ]
東洋精機キャピログラフ１Ｂ型を用いて、温度３２０℃、せん断速度 ｒ＝１０００ｓｅｃ-1条件下で測定した。
【００３１】
[面積収縮率]
熱処理後不織布のタテ方向とヨコ方向、２０ｃｍ角の３００℃×１時間後の面積での収縮率を表す。
【００３２】
実施例１
ｐ−ヒドロキシ安息香酸と２−ヒドロキシナフタレン−６−カルボン酸との共重合体からなる溶融液晶性ポリエステル[ポリプラスチックス社製 Ｌ−９５０、融点３００℃、溶融粘度２１Ｐａ・ｓ（温度３２０℃・せん断速度１０００sec-1下）]を用い、紡糸温度３１０℃、一次エアー温度３１０℃でメルトブローン紡糸し、目付７３．２g/m2、タテ裂断長０．０７Ｋｍ、厚さ０．５５９ｍｍ、密度０．１３g/cm3、平均繊維径６．３μｍの物性を持つ不織布を得た。ついで該不織布にロール温度１３０℃、線圧１００ｋｇ／ｃｍでカレンダー処理を行い、厚さ０．１３ｍｍ、密度０．６７４g/cm3、タテ裂断長１．００Ｋｍの中間物性を得た。その後、窒素雰囲気中で２５０℃×５ｈｒ＋２７５℃×２０ｈｒで熱処理を行った。不織布のタテ裂断長４．０Ｋｍ、ヨコ裂断長２．２Ｋｍ、面積収縮率０．１％で満足できるものであった。
【００３３】
実施例２
実施例１と同じ溶融液晶性ポリエステルを用い、ブローン条件を変更して平均繊維径は８．８μｍ、目付６６g/m2、厚さ０．４６７ｍｍ、密度０．１４１g/cm3のメルトブローン不織布を得、次にカレンダー処理として温度１８０℃、線圧１５０ｋｇ／ｃｍを施し、厚さ０．１１４ｍｍ、密度０．５７９g/cm3の中間物性を得た。次に実施例１と同じ条件で熱処理を行った。得られた不織布はタテ裂断長５．２Ｋｍ、ヨコ裂断長４．３Ｋｍ、収縮率０％で良好な物性となった。
【００３４】
比較例１
実施例２と全く同じ不織布を用い、次にカレンダー処理として、温度７０℃、線圧３０ｋｇ／ｃｍを施し、次に窒素雰囲気中、２５０℃×５ｈｒ＋２７５℃×２０ｈｒで熱処理を行った。できた不織布はタテ裂断長２．５Ｋｍ、ヨコ裂断長１．２Ｋｍ、収縮率３％で粗雑で後の工程に耐える物性ではなかった。
【００３５】
比較例２
実施例２と全く同じ不織布を用い、次に温度３２５℃、線圧２５０ｋｇ／ｃｍでカレンダー処理する途中、不織布が溶融を起こしロールに捲きついて中止した。
実施例および比較例の平均繊維径、カレンダー条件、不織布物性を表１に示す。
【００３６】
【表１】
実施例３
実施例１と同じポリマー組成を有しする溶融液晶性ポリエステルであってロットナンバーの異なるポリマー[ポリプラスチックス社製 Ｌ−９５０、融点３０２℃、溶融粘度１１Ｐａ・ｓ（温度３２０℃・せん断速度１０００sec-1下）]を用い、実施例１と同様にしてメルトブローン紡糸を行ない、ショットの無い地合良好なメルトブローン不織布を得た。不織布の平均繊維径７．７μｍ、目付７３g/m2、厚さ０．５６mm、密度０．１３g/cm3、タテ裂断長 ０．０７Ｋｍ、巾方向の目付斑（ＣＶ）２．１％であった。次いでこの不織布を温度１５０℃、線圧１３０ｋｇ／ｃｍでカレンダーがけし、その後、熱処理釜で２５０℃×５ｈｒ＋２８５℃×２０ｈｒ熱処理した。得られた不織布はタテ裂断長５．２Ｋｍ、ヨコ裂断長３．１Ｋｍ、面積収縮率０．２％の強力と寸法安定性を備えていた。
【００３８】
実施例４
熱処理条件を２４０℃×１０ｈｒ＋３００℃×２０ｈｒに変更すること以外は実施例３と全く同じにした。得られた不織布はタテ裂断長６．５Ｋｍ、ヨコ裂断長４．９Ｋｍ、面積収縮率０％の高水準のものであった。
【００３９】
実施例５
熱処理条件を２５０℃×５ｈｒ＋２７５℃×５ｈｒに変更すること以外は実施例３と全く同じにした。得られた不織布はタテ裂断長３．３Ｋｍ、ヨコ裂断長１．７Ｋｍ、面積収縮率０．３％で物性を満足していた。
【００４０】
比較例３
熱処理条件を２５０℃×２４ｈｒとすること以外は実施例３と全く同じにした。しかし得られた不織布はタテ裂断長２．４Ｋｍ、ヨコ裂断長０．６Ｋｍ、面積収縮率２％の弱い不織布となり後の工程に耐えるものではなかった。
【００４１】
比較例４
熱処理条件を３３０℃×２４ｈｒとすること以外は実施例３と全く同じにした。しかし熱処理後不織布は積層した接触部分が融着を起こし解除不能となり作業を中止した。
実施例および比較例のカレンダー条件、熱処理条件、不織布物性を表２に示す。
【００４２】
【表２】
実施例のものは工程通過性に耐えるタテ・ヨコの強力と熱収縮率を充分満足するするものでものであったが、比較例では、不織布どうしの接着を起したり、工程通過性に耐えるタテ・ヨコの強力及び熱収縮率全てを満足するものでは無かった。
【００４４】
【発明の効果】
本発明の溶融液晶性ポリエステル繊維からなる不織布は、バインダー成分を含んでおらず、タテ及びヨコ強力のバランスが良く、耐熱性・低吸湿性にも優れており、薄厚で精密を要する材料(例えば電気絶縁材料としてのプリント配線基板)に好適である。また、例えば、耐切創性を生かした防護衣料、振動減衰性を生かしたスポーツ用品、衝撃吸収性を生かしたショックアブソーバーや各種産業資材不織布として多様な利用が可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nonwoven fabric made of a fused anisotropic aromatic polyester fiber and effective as a protective material, a soil condition improving material, a vibration material, an abrasive, an electrical insulating material and the like.
[0002]
[Prior art]
Wet nonwoven fabrics and dry nonwoven fabrics are the mainstream technologies for producing nonwoven fabrics from organic fibers, but wet nonwoven fabrics do not have strength as they are, so fibrillated fibers and binder fibers are mixed and then entangled. , Heat treatment and water entanglement treatment etc. must be performed, the process becomes complicated and the manufacturing cost increases, and for example, there is an increased possibility of mixing in foreign matters (metals / dissimilar fibers) that are problematic for electrical insulation materials, etc. To do. Also, dry nonwoven fabrics are not suitable for substrates for printed wiring boards that have poor formation and require high accuracy.
On the other hand, a spunbond method for producing a nonwoven fabric by spinning directly using melted liquid crystal polyester has been proposed in Japanese Patent Application Laid-Open No. 6-128857, and calender treatment and heat treatment are performed using a spunbond nonwoven fabric of melted liquid crystal polyester. A method is described. However, since the spunbond method opens the filament after spinning, the fibers are not fused at the entanglement point, and a binder component is required. If the melted liquid crystalline polyester is used alone, it is impossible to fuse only the fiber entanglement point even if it is calendered and heat-treated, and the nonwoven fabric itself will be fused to form a film. When rolled by calendering at a temperature around the melting point of the polymer, the polymer softens due to the roll linear pressure, and the nonwoven fabric stretches smoothly. On the other hand, if it is not pulled, it will shrink and will not be in a stable form. Therefore, by heat treatment at a temperature below the melting point, the crystallization of the filament itself increases and the warp direction of the nonwoven fabric becomes stronger, but the transverse direction is very weak because there is no fusion of the fiber entanglement points. One direction is strong, but the opposite direction is very weak.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems of the strength and non-contamination of a nonwoven fabric made of a molten liquid crystal polyester as described above.
[0004]
[Means for Solving the Problems]
That is, the present invention is composed of a molten liquid crystalline polyester fiber containing 60% or more of fibers having an average fiber diameter of 0.6 to 20 μm, and has a length in the vertical direction of 1.5 km or more and an area at 300 ° C. for 1 hour. A melt-blown nonwoven fabric characterized by a shrinkage rate of 3% or less, and the present invention melts and spins molten liquid crystalline polyester, and at the same time blows off the spun product with a high-temperature high-speed fluid and accumulates it on the collecting surface. When the nonwoven fabric is manufactured by subjecting the web to calendering and heat treatment, the nonwoven fabric has a surface temperature of 90 ° C. or higher and a melting point of the molten liquid crystalline polyester, a linear pressure of 50 kg / cm to 200 kg / gap a (cotter) provided between the calender rolls in cm or less, perform the calendering in the before and after product plans thickness gap, (fusion of the molten liquid crystalline polyester Temperature -40 ° C.) or higher, (melting point + 20 ° C.) The following method for producing a melt-blown nonwoven fabric made of liquid crystalline polyester fiber characterized in that the heat treatment over 3 hours at temperature.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The molten liquid crystalline polyester referred to in the present invention is a polymer obtained by polymerization from aromatic diol, aromatic dicarboxylic acid, aromatic hydroxycarboxylic acid or the like, and exhibits optical anisotropy (liquid crystallinity) in the molten phase. It is a fiber made of things. Such characteristics can be easily recognized by heating the sample on the hot stage in a nitrogen atmosphere and observing the transmitted light.
[0006]
The molten liquid crystalline polyester used in the present invention comprises, for example, a combination of repeating structural units represented by the following chemical formulas 1 and 2.
[0007]
[Chemical 1]
Particularly preferred is an aromatic polyester in which the portion consisting of the repeating structural units (A) and (B) shown in the following chemical formula 3 is 65 mol% or more, and particularly the component (B) is 4 to 45 mol%. Aromatic polyesters are preferred.
[0009]
[Chemical 3]
The polyester may contain other polymers or additives as long as the strength does not substantially decrease.
[0011]
Next, the nonwoven fabric made of molten liquid crystalline polyester fiber referred to in the present invention is a melt blown nonwoven fabric, and melt molten liquid crystalline polyester is melted and spun from a nozzle, and at the same time, the molten liquid crystalline polyester is refined into fine fibers by high temperature and high pressure gas. It is a nonwoven fabric produced by being collected on a collecting surface (for example, a wire mesh) which is blown away and sucked.
[0012]
However, melt blown nonwoven fabrics using conventional molten liquid crystalline polyester are high melting point polymers, solidify quickly, and because of high viscosity, it is difficult to make a satisfactory nonwoven fabric product that can only be used as an intermediate and screw, and preferably, It is preferable to use a molten liquid crystalline polyester having a melting point of 280 ° C. or more and a melt viscosity of 25 Pa · s or less, particularly preferably 20 Pa · s (temperature 320 ° C. and shear rate 1000 sec −1 ). A nonwoven fabric meltblown using such a polyester has good formation, heat resistance, dimensional stability, low water absorption, and resin impregnation.
[0013]
The average diameter of the fibers accumulated on the collecting surface by the melt blown method is determined by the nozzle diameter, the discharge amount, and the air speed. In the present invention, the average fiber diameter is 0.6 to 20 μm, preferably 1 to 15 μm. Particularly, 60% or more of fibers having a size of 1 to 10 μm are contained, and strength, flexibility and breathability are provided. In addition, in this invention, an average fiber diameter refers to the average value of the value which magnified and imaged the nonwoven fabric with the scanning electron microscope, and measured the diameter of arbitrary 100 fibers.
[0014]
In addition, the accumulated nonwoven fabric is more likely to have spotted spots as it is made thinner, and more likely to appear in the horizontal direction than in the vertical direction. To express this unevenness, it is expressed by CV (%) value. When the CV (%) value is 3% or more, the thin part becomes insufficient in strength, and it does not become a satisfactory product because it adversely affects process passability and product physical properties. 2% or less.
[0015]
Next, in the present invention, after the melt blown, the roll temperature is set on the offline or online conveyor so that the surface of the nonwoven fabric is 90 ° C. or more exceeding the glass transition point of the polymer, the melting temperature of the molten liquid crystalline polyester is below, the linear pressure is 50 kg. It is desirable to perform calendar processing at / cm or more and 200 kg / cm or less.
The calendar process may be online or offline, but online is preferable. In general, when a nonwoven fabric is calendered at a temperature of less than 90 ° C., the temperature does not reach the glass transition point of the melted liquid crystalline polyester forming the nonwoven fabric, so that the fibers are not deformed and fixed and the strength is increased. Absent. For this reason, the desired thickness is gradually restored to the original thickness and the required product thickness is not achieved.
[0016]
On the other hand, when the calender roll temperature exceeds the melting point of the molten liquid crystalline polyester, the nonwoven fabric melts and adheres to the roll, and roll seizure occurs.
[0017]
In order to make the thickness of the resulting nonwoven fabric more uniform, it is preferable to provide a gap (cotter) between the calender rolls and calender the gap between before and after the planned product thickness.
[0018]
If the roll linear pressure during calendering is less than 50 kg / cm, there is little roll pressing, and the nonwoven fabric will return to its original thickness after a while without deformation and fixing of the fiber entanglement point. A nonwoven fabric cannot be formed. In addition, in order to perform the next heat treatment, a bulky heat treatment machine is necessary if the bulk remains high, resulting in an increase in cost.
[0019]
On the other hand, when the roll linear pressure exceeds 200 kg / cm, the entanglement increases, but buckling occurs, the fiber entanglement point is crushed, the shape of the nonwoven fabric is poor, and the process passability is deteriorated. . Therefore, it is desirable to calender the nonwoven fabric at a surface temperature of 90 ° C. or higher and lower than the melting temperature of the molten liquid crystalline polyester and a linear pressure of 50 kg / cm to 200 kg / cm.
[0020]
In the present invention, after the calendar treatment, the nonwoven fabric is heat-treated in a high-temperature gas at a temperature of (melting temperature of molten liquid crystalline polyester−40 ° C.) or more and (melting temperature + 20 ° C.) or less for 3 hours or more. Preferably, the heat treatment is performed for 3 hours or more and 72 hours or less, and the strength of the nonwoven fabric in the vertical and horizontal directions is increased by advancing the orientation of the fiber entanglement points and the fibers themselves.
[0021]
When heat treatment is performed at a temperature lower than (melting temperature of molten liquid crystalline polyester−40 ° C.), solid-state polymerization of the molten liquid crystalline polyester caused by the heat treatment does not proceed, and the heat treatment takes time, and the strength of the nonwoven fabric is improved. This is not possible. Conversely, if the heat treatment temperature is increased beyond (melting temperature of molten liquid crystalline polyester—40 ° C.), the fiber entanglement point and the orientation of the fiber itself advance, and the strength of the nonwoven fabric increases. The heat treatment temperature is preferably (melting temperature of molten liquid crystalline polyester—30 ° C.) or higher, more preferably (melting temperature of molten liquid crystalline polyester—20 ° C.) or higher.
[0022]
On the other hand, when the heat treatment temperature exceeds (the melting point temperature of the molten liquid crystalline polyester + 20 ° C.), the molten liquid crystalline polyester softens and the fiber starts to melt, and the fibers adhere to each other to form a film. For this reason, there is a problem that air permeability and flexibility are lost, or, for example, when resin impregnation is performed in a subsequent process, the impregnation property is deteriorated and the impregnation rate is lowered.
[0023]
As the gas used as the heating medium, a mixed gas such as nitrogen, oxygen, argon, carbon dioxide, air, or the like is used. The gas to be used preferably has a dew point of -20 ° C or lower. The heat treatment may be under tension or without tension depending on the purpose. Thus, after the calendar treatment, the non-woven fabric is heat-treated in a heated gas at a temperature not lower than (melting temperature of molten liquid crystalline polyester−40 ° C.) and not higher than (melting temperature of molten liquid crystalline polyester + 20 ° C.). The fiber entanglement point that has already been point-fused at the fiber intersection and the orientation of the fiber itself are advanced to make the warp and transverse directions of the nonwoven fabric highly strong.
[0024]
The heat-treated non-woven fabric exhibits an area shrinkage of 3% or less, preferably 2% or less after 300 ° C. × 1 hour, excellent dimensional stability, and high heat resistance with a melting point of 325 ° C. or more, It has excellent physical properties such as a vertical fracture length of 2.5 km or more and a horizontal fracture length of 1.5 km or more. If the quality is inferior to this, the passability of the post-process becomes poor or it cannot be used for industrial materials that require accuracy.
[0025]
In the present invention, since steps such as pulping, cutting, and papermaking, which are essential when producing a wet nonwoven fabric, are not required, there is less concern about foreign matter (metal) being mixed into the nonwoven fabric in the process. It can be used as an insulating material. In addition, the spunbond method requires thick denier, lamination with binder binder or other binder nonwoven fabric, and is not suitable for thin and precise materials. This is possible even without the use of a binder.
[0026]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these description items. The measured numerical values described in the examples and comparative examples were obtained by the following method.
[0027]
[Breaking length km]
The strength of DRY in the MD direction with a width of 15 mm and a sample length of 4 cm was measured to determine the breaking length.
[0028]
[Mouth spots (CV)%]
The cut weight is continuously cut into 5 cm squares, and the weight is measured by CV as spotted spots. Here, CV (%) = σn / average value × 100
[0029]
[Melting point ℃]
A 10 mg sample is taken in a DSC (for example, TA3000 manufactured by Mettler), sealed in an aluminum pan, nitrogen is flowed at 50 cc / min, the temperature is increased at a rate of 20 ° C./min, and the endothermic peak temperature is measured. When a clear peak temperature does not appear in the 1st run, the temperature is raised to 50 ° C / min. After completely melting for about 3 minutes at a temperature 50 ° C higher than the expected melting point, cool to 80 ° C / min to 50 ° C. After that, the measurement is performed at a temperature rising rate of 20 ° C./min.
[0030]
[Melt viscosity Pa · s]
Using a Toyo Seiki Capillograph Type 1B, measurement was performed under the conditions of a temperature of 320 ° C. and a shear rate of r = 1000 sec −1 .
[0031]
[Area shrinkage]
The shrinkage rate in the length direction of a nonwoven fabric after heat processing, a horizontal direction, and the area of 300 degreeC x 1 hour of a 20 cm square is represented.
[0032]
Example 1
Melt liquid crystalline polyester made of a copolymer of p-hydroxybenzoic acid and 2-hydroxynaphthalene-6-carboxylic acid [manufactured by Polyplastics L-950, melting point 300 ° C., melt viscosity 21 Pa · s (temperature 320 ° C. shear rate 1000sec using -1 below)], a spinning temperature 310 ° C., and melt blown spun at primary air temperature 310 ° C., basis weight 73.2 g / m 2, vertical breaking length 0.07Km, thickness 0.559 mm, density 0 A nonwoven fabric having physical properties of .13 g / cm 3 and an average fiber diameter of 6.3 μm was obtained. Next, the nonwoven fabric was calendered at a roll temperature of 130 ° C. and a linear pressure of 100 kg / cm to obtain intermediate physical properties of a thickness of 0.13 mm, a density of 0.674 g / cm 3 , and a vertical tear length of 1.00 Km. Thereafter, heat treatment was performed at 250 ° C. × 5 hr + 275 ° C. × 20 hr in a nitrogen atmosphere. The nonwoven fabric was satisfactory with a vertical tear length of 4.0 km, a lateral tear length of 2.2 km, and an area shrinkage of 0.1%.
[0033]
Example 2
Using the same molten liquid crystalline polyester as in Example 1, the blown conditions were changed to obtain a meltblown nonwoven fabric having an average fiber diameter of 8.8 μm, a basis weight of 66 g / m 2 , a thickness of 0.467 mm, and a density of 0.141 g / cm 3. Next, as a calendar treatment, a temperature of 180 ° C. and a linear pressure of 150 kg / cm were applied to obtain intermediate physical properties of a thickness of 0.114 mm and a density of 0.579 g / cm 3 . Next, heat treatment was performed under the same conditions as in Example 1. The obtained nonwoven fabric had good physical properties with a vertical tear length of 5.2 km, a horizontal tear length of 4.3 km, and a shrinkage rate of 0%.
[0034]
Comparative Example 1
The same non-woven fabric as in Example 2 was used. Next, as a calendar process, a temperature of 70 ° C. and a linear pressure of 30 kg / cm were applied, and then a heat treatment was performed in a nitrogen atmosphere at 250 ° C. × 5 hr + 275 ° C. × 20 hr. The resulting non-woven fabric had a vertical tear length of 2.5 Km, a horizontal tear length of 1.2 Km, a shrinkage rate of 3%, and was not rough and could not withstand the subsequent steps.
[0035]
Comparative Example 2
The same nonwoven fabric as in Example 2 was used, and then during the calendar treatment at a temperature of 325 ° C. and a linear pressure of 250 kg / cm, the nonwoven fabric melted and stuck to the roll, and was stopped.
Table 1 shows the average fiber diameter, calendar conditions, and nonwoven fabric properties of the examples and comparative examples.
[0036]
[Table 1]
Example 3
Polymers having the same polymer composition as in Example 1 and having different lot numbers [Polyplastics L-950, melting point 302 ° C., melt viscosity 11 Pa · s (temperature 320 ° C., shear rate 1000 sec) -1 lower)] was used, and melt blown spinning was carried out in the same manner as in Example 1 to obtain a melt blown nonwoven fabric having no formation of shots. Non-woven fabric with an average fiber diameter of 7.7 μm, basis weight of 73 g / m 2 , thickness of 0.56 mm, density of 0.13 g / cm 3 , vertical tear length of 0.07 Km, and fabric weight in the width direction (CV) of 2.1% there were. Next, this nonwoven fabric was calendered at a temperature of 150 ° C. and a linear pressure of 130 kg / cm, and then heat-treated in a heat treatment pot at 250 ° C. × 5 hr + 285 ° C. × 20 hr. The obtained non-woven fabric had strength and dimensional stability with a vertical tear length of 5.2 km, a lateral tear length of 3.1 km, and an area shrinkage of 0.2%.
[0038]
Example 4
Except for changing the heat treatment condition to 240 ° C. × 10 hr + 300 ° C. × 20 hr, it was exactly the same as Example 3. The obtained non-woven fabric was of a high level with a vertical tear length of 6.5 km, a lateral tear length of 4.9 km, and an area shrinkage of 0%.
[0039]
Example 5
Except for changing the heat treatment condition to 250 ° C. × 5 hr + 275 ° C. × 5 hr, it was exactly the same as Example 3. The obtained nonwoven fabric satisfied the physical properties with a vertical tear length of 3.3 km, a horizontal tear length of 1.7 km, and an area shrinkage of 0.3%.
[0040]
Comparative Example 3
The heat treatment conditions were exactly the same as in Example 3 except that the heat treatment conditions were 250 ° C. × 24 hr. However, the obtained nonwoven fabric was a weak nonwoven fabric having a vertical tear length of 2.4 km, a lateral tear length of 0.6 km, and an area shrinkage of 2%, and could not withstand subsequent processes.
[0041]
Comparative Example 4
The heat treatment conditions were exactly the same as in Example 3 except that the heat treatment conditions were 330 ° C. × 24 hr. However, after the heat treatment, the laminated non-woven fabric caused fusion at the contact portion, so that the work could not be released.
Table 2 shows the calendar conditions, heat treatment conditions, and nonwoven fabric properties of the examples and comparative examples.
[0042]
[Table 2]
In the examples, the vertical and horizontal strength and heat shrinkage ratio that withstand the process passability were sufficiently satisfied, but in the comparative example, the non-woven fabrics were bonded to each other, and the warp resistance to the process passability was achieved. -It did not satisfy all of the horizontal strength and heat shrinkage rate.
[0044]
【The invention's effect】
The nonwoven fabric made of the melted liquid crystalline polyester fiber of the present invention does not contain a binder component, has a good balance of vertical and horizontal strength, is excellent in heat resistance and low moisture absorption, is thin and requires precision (for example, It is suitable for a printed wiring board as an electrically insulating material. Also, for example, it can be used in various ways as protective clothing that makes use of cut resistance, sports equipment that makes use of vibration damping, shock absorbers that make use of shock absorption, and various industrial material nonwoven fabrics.
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| US11312829B2 (en) | 2019-01-04 | 2022-04-26 | Taiwan Union Technology Corporation | Flexible prepreg and uses thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2006144141A (en) * | 2004-11-17 | 2006-06-08 | Kuraray Co Ltd | Substrate material for heat-resistant adhesive tape |
| JP4229293B2 (en) | 2006-06-12 | 2009-02-25 | 株式会社立花商店 | Manufacturing method of cleaning web, cleaning web, image forming apparatus, and fixing device |
| JP4980107B2 (en) * | 2007-03-22 | 2012-07-18 | 株式会社クラレ | Substrate for resin reinforcement and manufacturing method thereof |
| JP4916984B2 (en) * | 2007-09-19 | 2012-04-18 | 株式会社クラレ | Non-woven |
| JP4916985B2 (en) * | 2007-09-20 | 2012-04-18 | 株式会社クラレ | Non-woven |
| JP5812786B2 (en) * | 2011-09-27 | 2015-11-17 | 株式会社クラレ | High strength nonwoven fabric |
| JP2013159887A (en) * | 2012-02-09 | 2013-08-19 | Kuraray Co Ltd | High performance wiping material with excellent durability |
| JP6344864B2 (en) * | 2013-03-14 | 2018-06-20 | 株式会社立花商店 | Cleaning web, method for producing melt blown nonwoven fabric, method for producing cleaning web, image forming apparatus and fixing device |
| JP6310364B2 (en) * | 2014-08-21 | 2018-04-11 | 株式会社クラレ | Conductive nonwoven fabric and method for producing melt blown nonwoven fabric used therefor |
| KR102180649B1 (en) | 2014-08-22 | 2020-11-19 | 주식회사 쿠라레 | Conductive nonwoven fabric and manufacturing method for melt-blown nonwoven fabric used in conductive nonwoven fabric |
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| US11312829B2 (en) | 2019-01-04 | 2022-04-26 | Taiwan Union Technology Corporation | Flexible prepreg and uses thereof |
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