JP2004500169A - Method for improving creep resistance of substrate composite - Google Patents

Abstract

It has been found that the uniformity and strength of the bond between one or more elastic strands and one or more base materials in a substrate composite is improved by heating the strands. By heating one or more elastic strands prior to bonding, the creep resistance, which is a measure of the uniformity and strength of the bond between the elastic strands and the base material, is about 5%, especially 10%, more particularly Typically about 15% increase. Accordingly, the present invention is directed to improving the uniformity and strength of the bond between the elastic strand and the base material by heating the strand before bonding. The strands can be heated by heat conduction and / or convection, by an irradiative method incorporating, for example, infrared radiation or microwave radiation, or by some combination thereof. If the elastic strand is manufactured at a different location than where the strand is used as a raw material, the strand may be heated at either location. In addition, the strands can be heated in-line, i.e., as part of the strand manufacturing process or using the strands as raw material, or off-line, i.e., in a step different from any of the foregoing. You can also.

Description

　サンプルの初期クリープを求めた後に、基体複合材７６（厚紙にステープル留めされている）を、華氏１００度の温度になるまで予め加熱された強制空気乾燥器に入れた。９０分後、乾燥器から基体複合材と厚紙を取り出した。次いで、およそ１０分間、基体複合材を冷却させた。ここでさらに収縮したストランドの長さを測定した。
１７５ｍｍと最後に収縮したストランドの長さ７８すなわちＹ_{ｆｉｎａｌ}との差を用いてサンプルの「最終クリープ」を計算した。本発明において、最終クリープは次式を用いて計算される。

　本発明の目的に係るクリープ抵抗又はクリープ抵抗値は、次のようにして計算される。
クリープ抵抗、％＝１００−最終クリープ　　　　　　　　　　［式３］
【００３７】
着用者の身体の付近に装着される使い捨て吸収体物品において、人間の体温が華氏約９８度であることから、最終クリープは、使用中の物品の性能の尺度を与える。仮想の状況は、この測定の意義についての詳細を与える。２つのベース材料又は折り畳まれた１つのベース材料の間に３本の弾性ストランドが挟み込まれた状態で、基体複合材が作製されると仮定する。また、接着剤を用いてベース材料にストランドを付着することにより、ストランドが細長い形状、通常は約２００％から約３００％までの伸長量のラミネートが作製されると仮定する（次の実施例と、どのようにして弾性ストランドを組み入れた基体複合材を作製するのかの詳細について、その本発明に係る部分を引用により組み入れる、発明の名称「エラストマー・ラミネート・ウェブを作製する方法及び装置」の米国特許第５，９６４，９７３号参照）。華氏１００度で９０分間エージングした後に、各ストランドの長さの大部分に付着している接着剤とベース材料から弾性ストランドが剥がれ、ストランドが収縮する場合には、最終クリープは比較的高く、クリープ抵抗は比較的低いものとなる。剥がしたストランドが収縮して呈する張力が小さく、基体複合材の長さに沿って比較的均一の仕上りで１つ又はそれ以上のベース材料に寄せるギャザーは僅かであることから、エラストマー複合体としての基体複合材の性能は低くなる。
【００３８】
第２の仮定状況において、基体複合材が、前のパラグラフで説明したようにして作製されると再び仮定する。また、ストランドが、接着剤を用いて１つ又はそれ以上のベース材料に取り付けられると仮定する。華氏１００度で９０分間エージングした後に、弾性ストランドが、各ストランドの長さの大部分に沿ってベース材料に均一に付着されたままである場合には、最終クリープは比較的低く、クリープ抵抗は比較的高いものとなる。ストランドが、収縮して基体複合材の長さに沿って比較的均一の仕上りで１つ又はそれ以上のベース材料にギャザー寄せすることから、エラストマー複合体としての基体複合材の性能は高くなる。
【００３９】
次の実施例は、弾性ストランドの加熱により、最終クリープ値が減少する、すなわち加熱した弾性ストランドを組み入れた基体複合材のクリープ抵抗が向上することを示すものである。表１は、例えば２２．９％の最終クリープ値は、メルトブロー塗布技術を使用して７グラム毎平方メートル（すなわちｇｍ^−２）の塗布量でＨ‐２５２５Ａ接着剤を塗布した時の、２枚のスパンボンドウェブの間に挟み込まれた熱処理後のＧＬＯＳＰＡＮ８４０弾性ストランドについて得られた値である。ＧＬＯＳＰＡＮ８４０ストランドは、２００％の伸長状態でスパンボンドウェブに付着された。ＧＬＯＳＰＡＮ８４０は、マサチューセッツ州フォールリバーのグローブ・マニファクチャリング社により製造された弾性ストランド材料であり、ポリエステル‐ｂ‐ポリウレタンブロック共重合体からなる。通常は、スパンボンドウェブは、ポリプロピレン繊維から構成されており、１平方ヤード当たり０．５オンスの坪量を有するものである。しかしながら、対照用基体複合材は、同じ２２．９％の最終クリープ値を得るために、１０ｇｍ^−２のＨ２５２５Ａ接着剤の塗布量を必要とした。したがって、ＧＬＯＳＰＡＮ８４０弾性ストランドの熱処理により、所定の最終クリープ値を得るために必要とされる接着剤の量が減少した。
【００４０】
前の実施例は、ストランドをベース材料に付着する前に加熱することで、基体複合材のクリープ抵抗値を向上することができるということを示すものである。既に説明したように、弾性ストランドは、高温の空気すなわち対流熱伝達及び熱伝導、赤外線照射、又はこれらの幾つかの組み合わせによって、加熱することができる。弾性ストランド又は弾性ストランドのボビンが、別の処理ステップ（すなわちオフライン）で加熱される場合には、ストランド又はボビンは、強制空気乾燥器又は電子オーブンの中で、或いは赤外線電球の下で加熱することができる。これに対して、ストランドが、該ストランドを作製する又は該ストランドを原料として使用するプロセスの一部（すなわちインライン）として加熱される場合には、移動するストランドにマイクロ波照射、赤外線照射、高温の空気、又はこれらの幾つかの組み合わせを向けて該ストランドを加熱することができる。
【００４１】
乾燥器が、単にストランドを加熱することのみに使用される装置である場合には、ストランドは通常、該ストランドを作製するために使用されるプロセス、又は該弾性ストランドを原料として使用するプロセスとは別のステップで加熱されることになる。ストランドの加熱速度を増すために、乾燥器の温度を１００度よりも高く上昇させることもできるが、ストランドの構成ポリマーが劣化するので、温度をそれほど高くすることはできない。しかしながら、対流及び伝導に基づいてストランドを加熱する方法、例えばストランドに高温の空気を向けることは、１つ又はそれ以上の照射方法と組み合わせて、インラインでストランドを加熱することができる（後述する）ということに注目されたい。
【００４２】
ストランド製造プロセス又はストランドを原料として使用するプロセスとは別のステップ（即ちオフライン）で弾性ストランドを加熱するために、ストランドのスプール、ボビン、又はリールを、所定の温度の乾燥器の中に、所定の時間だけ入れることができる。或いは、このスプール、ボビン、又はリールに、所定の温度に加熱された空気を、所定の時間だけ向けることもできる。１９９９年１２月２２日に出願され、本発明に関係する部分を引用によりここに組み入れる（及び本出願の優先権主張の基礎となる）出願係属中の米国特許出願第６０／１７１，４６７号、発明の名称「弾性ストランドの強度特性を向上させる方法」に記載されるように、所定の温度で弾性ストランド材料が劣化したかどうかを分析技術を用いて確認することができる（後述の実施例参照）。
【００４３】
ストランドのスプール又はボビンは、弾性ストランドが製造された場所、又は（ストランドが使用される場所が、該ストランドが製造された場所とは異なる場合は）弾性ストランドが原料として使用される場所、のどちらかにおいて乾燥器の中に入れることができる。例えば、ストランドが製造された場所で、該ストランドを最初に巻き付けた後の弾性ストランドのボビンを、１０２度又はそれ以上の温度の強制空気乾燥器の中に、２時間又はそれ以上入れることができる。或いは、より一層高い温度の強制空気乾燥器の中に、これより短い間だけ入れることもできる。ストランドを熱処理した後に、このボビンは、輸送のために準備されることもあるし、輸送の前に幾らかの期間だけ保管されることもある。
【００４４】
ストランドを加熱するために、他の手法を用いることもできる。例えば、ストランドに照射するために、該弾性ストランドの近傍に赤外光源を配置することができる。赤外光源の一例は、ニュージャージー州レクアンノックのＴｅｃｈｎｉＬａｂ Ｉｎｓｔｒｕｍｅｎｔｓ，Ｉｎｃ．から入手可能な２５０Ｗの赤外線電球である。ストランドのポリマー成分は、赤外線を吸収すると熱を生じ、これによりストランドが加熱される。さらに、押出又は紡糸した後に、しかしボビンに初めて巻き付けられる前に（即ち弾性ストランドの製造場所におけるインラインで）、ストランドの近傍に１つ又は複数の赤外光源を配置することができる。ボビンが繰り出され、処理され、次いで再び巻き付けられる別の処理ステップが行われる場合には、この別の処理ステップの間に、１つ又は複数の赤外光源を用いてストランドを熱処理することができる。
【００４５】
或いは、弾性ストランドにマイクロ波放射を照射して、該ストランドを加熱することもできる。好適なマイクロ波発生器とキャビティは、１９９６年７月１６日発行のヘドリック他の米国特許第５，５３６，９２１号に記載されており、引用によりここに組み入れる。この装置は、シート状の材料をオンラインで処理するのに有用であり、また弾性ストランドをインラインで処理するのに用いることもできる。この装置は、ニューヨーク州アーモンク市所在のインターナショナル・ビジネス・マシンズ社から入手可能な、円筒形の単一モード共振性空胴マイクロ波アプリケータ（モデルＴＭ１０１）を備えている。このモデルのアプリケータの直径は、４インチであり、出力電力は、周波数２４５０ＭＨｚにおいて６．０ｋＷまで無段階調節できる。弾性ストランドをキャビティの中に導き、キャビティ内で該ストランドが複数のマイクロ波の定在波に曝されるようにすることができる。弾性材料が定在波の中を通過するに伴い、入射したマイクロ波のエネルギーは、該ストランド内で熱に変換される。ストランドではなくウェブを連続的に処理するためのマイクロ波発生器の使用例が、米国特許第５，９１６，２０３号に記載されており、本発明に関係する部分を引用によりここに組み入れる。これと同じ手法を用いて１つ又は複数の弾性ストランドを加熱することができる。
【００４６】
１つ又は複数の弾性ストランドを加熱するために、前述の特定の方法の１つ又はそれ以上を組み合わせて用いることもできる。例えば、１つ又は幾つかの赤外光源を、ストランドを加熱するために該ストランドに向けられる高温の空気流と組み合わせて使用することができる。すなわち、前述のように該ストランドをキャビティ内でマイクロ波放射に曝す前に又は曝した後に、該ストランドに高温の空気流を向けることができる。エネルギーを弾性ストランドに伝達してストランドを加熱させ、これにより、加熱したストランドを組み入れた基体複合材のクリープ抵抗を向上させる（又は最終クリープ値を減少させる）方法のいずれの組み合わせも本発明に包含される。
【００４７】
出願係属中の米国特許出願第６０／１６６３４８号に記載されるように、幾つかの場合において、最初に巻き付けられた後の弾性ストランドのボビンは、ボビンを巻き出し、ストランドを処理し、次いで再びストランドを巻き付けることによる幾つかの手法で加工又は処理することができる。この出願係属中の出願はまた、ストランドの強度の低下を抑えるために、水蒸気に対する弾性ストランドの露出を調整することが記載されている。したがって、ストランドの製造業者によって熱処理された弾性ストランドをさらに、熱処理されたストランドの水蒸気に対する露出を調整するような方法で処理し、保管し、扱う又は輸送することができる。
【００４８】
出願係属中の米国特許出願第６０／１６６３４８号は、複数の実施例を与え、これにより水蒸気に対する弾性ストランドの露出を調整することができる。これらと同じ方法を、熱処理前、熱処理後、又は熱処理の前後両方の弾性ストランドに用いることができる。弾性ストランドが既に熱処理されている場合には、熱処理されたストランドのボビン、スプール、又はリールを、湿度制御又は温度制御された部屋又は施設の中で保管することができる。これらのボビンが別の場所に輸送される場合には、該ボビンは、耐水蒸気透過性の障壁材料を含むコンテナの中に積み込むことができる。弾性ストランドを、低湿度環境において障壁材料を含むコンテナの中に入れる場合には、コンテナ内部における弾性ストランドの周囲の微視的環境は、この低湿度環境に対応するものとなる。コンテナを閉じた（例えばプラスチック袋をヒートシールした）後に、コンテナ外部の湿度又は温度が調整されない次の処理ステップを行うことができる。このコンテナは、製造プロセスにおいて弾性ストランドが原料として使用されるまで、開けられることはない。
【００４９】
出願係属中の米国特許出願第６０／１６６３４８号に開示されるように、障壁材料を含むコンテナを閉じる前に、熱処理された弾性ストランドを含む弾性ストランドの近くに、乾燥剤を入れることができる。コンテナが弾性ストランドの中に及び周りに水蒸気を侵入させるまで、この乾燥剤は、水蒸気を優先的に吸着又は吸収するように機能する。したがって、乾燥剤は、強度の劣化を最小限にする程度にコンテナ内部の湿度を維持するのを助ける。
【００５０】
別の態様において、障壁材料を含むコンテナを閉じる前に、同じく既に熱処理された弾性ストランドと共に、湿度検出器又は湿度計を入れる。弾性ストランドの購入者まで輸送された後、この袋又はコンテナを開ける時に、コンテナ内部の湿度が特定の値を超えていたかどうかを判断するため湿度検出器を調べることができる。湿度が特定の値を超えていた場合は、袋又はコンテナを受け取らずに仕入先に返品することができる。或いは、輸送品からサンプルを直ちに試験することもできる。ストランドの強度特性が条件を満たしているとみなされた場合には、輸送品を受理し、原料として使用することができる。
【００５１】
ストランドの製造場所で該ストランドを加熱せずに、ストランドが原料として使用される場所で弾性ストランドのボビンを加熱することができる。弾性ストランドが、障壁材料を含む密封されたコンテナに入れて輸送されない場合には、該弾性ストランドは、受理された時に、又は保管した後でストランドが原料として使用される前に、加熱することができる。弾性ストランドが使用前に保管される場合には、出願係属中の米国特許出願第６０／１６６３４８号に開示されるように、温度制御又は湿度制御された環境内で該ストランドを保管することができる。
【００５２】
弾性ストランドが、障壁材料を有するコンテナに入れて輸送された場合は、該弾性ストランドは、コンテナを開けるまで加熱されない。したがって、例えば弾性ストランドのコンテナを、該コンテナが開けられるまでの間、保管することができる。コンテナを開けて弾性ストランドのボビンを取り出した後に、このボビンを選択された温度の乾燥器の中に、選択された時間だけ入れることができる。或いは、クリープ値の所望の増加を得るために、ボビンをマイクロ波オーブンの中に入れることもできる。ストランドをオフラインで加熱せずに、繰り出しスタンドと、基体複合材を製造するためベース材料にストランドを取り付ける位置との間の幾つかの場所（すなわちインライン）において、弾性ストランドにマイクロ波放射、赤外線放射、及び／又は高温の空気を当てることもできる。いずれの場合にも、データを使用して、所定のクリープ抵抗の向上を達成するのに必要な熱処理条件を選択することができる（例えば、後述の実施例は、最終クリープ又はクリープ抵抗における所定の変化を得るための熱処理条件を確かめることができることを示す）。
【００５３】
弾性ストランドの強度の劣化を抑えることについての更に詳細な説明
前述のように、基体複合材のクリープ抵抗を向上させる方法は、水又は水蒸気に対するストランドの露出を調整することにより弾性ストランドの強度の低下を抑える方法と組み合わせて用いることができる。水又は水蒸気に対するストランドの露出を調整することが可能な幾つかの代表的な方法について、更に詳細な説明を進める前に、幾つかの付加的な定義について検討することは有用である。比湿という用語は、一般に、水蒸気が含まれていない気体の単位質量当たり保持された水蒸気質量を指す。ここで用いられる「比湿」とは、水蒸気を含んでいない気体の単位質量当たり保持された水蒸気質量を指し、この気体は通常は空気である。相対湿度という用語は、一般に、気化温度における液体の蒸気圧と蒸気分圧との比を指す。これは普通、百分率で表され、相対湿度１００パーセントとは、その気体が蒸気で飽和されていることを意味し、相対湿度０パーセントとは、その気体が蒸気を含んでいないことを意味する。ここで用いられる「相対湿度」とは、ガス温度における水の蒸気圧に対する水蒸気分圧の比を指し、このガスは通常は空気である。ここでは、「湿度」とは、普通は空気である気体中の水蒸気量の尺度を指し、特に明記しない限り、比湿及び／又は相対湿度を指す。露点という用語は一般に、蒸気と気体との混合物が一定の湿度で冷却されて飽和することになる温度を指す。ここで用いられる「露点」という用語は、水蒸気と気体との混合物が一定の湿度で冷却されて飽和することになる温度を指し、この気体は通常空気である。
【００５４】
水蒸気に対するストランドの露出を調整することができる方法の１つは、湿度制御された環境における押出し又は紡糸の後に、１つ又はそれ以上の加工及び／又は処理ステップを行うことである。これは、１つ又はそれ以上の前記ステップを、選択された設定値を超えないように制御された筐体の湿度に対応する値の部屋、コンパートメント、その他の筐体の中で行うことでほぼ達成される。この設定値は、所望の比湿又は相対湿度に対応する。制御は一般に、最初にその筐体における比湿又は相対湿度に対応する値を感知する又は測定することを含む。湿度を感知又は測定するのに使用される装置は、通常、弾性ストランドの近傍に配置される。感知又は測定された値は、この感知又は測定された値を設定値と比較するコントローラ、コンピュータ、その他の装置に送信される。感知又は測定された値が設定値とかなり異なる場合は、筐体における比湿又は相対湿度が所望の感知又は測定された値に又はそれよりも下の値に強制的に調節されるように、制御動作が行われる。
【００５５】
通常は、比湿又は相対湿度は、混合物の温度が該混合物の露点より低く下がるように、冷却コイルを横切るように空気／水蒸気混合物を向けることで強制調節される。この冷却プロセスの結果として、水蒸気の一部がコイル上に凝結し、液体として除去され、これにより湿度が低下する。冷却コイルを横切るように十分な量の空気／水蒸気混合物を向け、次いで脱湿された空気を筐体に導くことで、湿度が所望のレベルに強制調節される。水蒸気が凝結し、この冷却プロセスにより除去された後に、空気を加熱して乾球温度を低下させることができる。ここで用いられる「乾球温度」とは、その混合物の中に入れた温度計によって示される空気／水蒸気混合物の温度を指す。したがって、ここで用いられる「湿度制御された」とは、比湿及び／又は相対湿度が制御された環境を指し、空気／水蒸気混合物が脱湿された後に、乾球温度を低下させるため空気が加熱される場合は、その環境の乾球温度はまた制御又は調整される。
【００５６】
空気／水蒸気混合物を、筐体内部から採取して脱湿し、次いでこの筐体に戻るように再循環させることもできるし、筐体外部から採取して脱湿し、筐体に入れること又はこの両方を行うこともできる。例えば筐体が、弾性ストランドが連続的に導かれる巻取り台の周りに形成される場合には、該筐体は、ストランドが進入し、巻き付けられるようにする開口を含む。製造環境が高温多湿である場合には、その開口から高温多湿の空気が入ってくる量を減らすために、筐体内部に僅かな正圧を維持することが好ましい。この場合には、正圧により開口から出ていく該筐体内部の空気／水蒸気混合物を取り戻すために、筐体外部の幾らかの量の空気／水蒸気混合物を脱湿し、該筐体の中に入れる必要がある。
【００５７】
設定値に又はそれより低くなるように湿度を制御するのではなく、最大比湿が或るレベルを超えないように、室内又は筐体内部の空気を設定温度まで冷却してもよい。大気圧における空気の湿度チャートを使用して、適切な設定温度を選択することができる。例えば、温度華氏４０度において相対湿度が丁度１００％のとき、その比湿は、乾燥空気のＩｂ_ｍ当たりの水蒸気量が約０．００６Ｉｂ_ｍとなる。この値は、６０日間後のピーク負荷値の６０％の低下の結果として得られた比湿の１／４より小さい（後述の実施例参照）。したがって、ここで用いられる「温度制御された」とは、弾性ストランドに曝される水蒸気量を調整するために、温度が或る値に制御される環境を指す。
【００５８】
前述のように、本発明の一実施形態は、押出し又は紡糸の後に、１つ又はそれ以上の加工及び／又は処理ステップの湿度を制御することに向けられる。或いは、空気の水蒸気保持量が制限されるように、１つ又はそれ以上の加工及び／又は処理ステップの温度を制御することもできる。例えば、巻取機において弾性ストランドが最初に巻き付けられるステップを、湿度制御又は温度制御された環境内で行うことができる。湿度制御又は温度制御された環境内で、第１巻取機の上流又は下流の処理ステップを行うこともできる。ここで用いられる「第１巻取機」とは、押出又は紡糸された後にストランドが最初に巻き付けられる巻取機を指し、「上流」とは、ストランドが押出し又は紡糸された後に、第１巻取機の前に行われる処理ステップを指し、「下流」とは、第１巻取機の後に行われる処理ステップを指す。別の巻出し／巻取り台（すなわち弾性ストランドが繰り出され、何らかの方法で処理され、再び巻取られる台）における第１巻取りステップの後に、１つ又はそれ以上の付加的な処理ステップを行う場合には、湿度制御及び温度制御された環境において、これらの１つ又はそれ以上の付加的な処理ステップを行うことができる。使用又は輸送の前に、弾性ストランドのボビンが保管される場合には、湿度制御又は温度制御された環境内でこのボビンを保管することができる。弾性ストランドが別の場所に輸送される場合には、弾性ストランドが繰り出され、次いで再び巻き付けられ、輸送のために包装される別のステップを含む弾性ストランドの準備ステップを、湿度制御又は温度制御された環境で行うこともできる。また、弾性ストランドを輸送又は輸送するステップ自体を、湿度制御又は温度制御された環境で行うことができる。
【００５９】
巻き付け、保管、（輸送が必要な場合には）輸送のための準備及び包装、輸送、並びにストランドが原料として使用されることになる場所で再び保管するこれらステップの全ては、製造機械上で原料として使用されるときのストランドの引張り強さが、最初に製造された時又は輸送のために準備された時のストランドの引張り強さから約２０％、特に約１０％、さらに特定的には約５％より多く減少しないように、湿度制御又は温度制御された環境内で行うことができる。
【００６０】
しかしながら、幾つかの場合、湿度制御又は温度制御された環境で全てのステップを行う必要はない。例えば、弾性ストランドを、障壁材料を有するコンテナに入れることができる。ここで用いられる「障壁材料」とは、水蒸気の侵入に対する抵抗性がある材料を指す。弾性ストランドを、障壁材料を有するコンテナ内に入れる、すなわち保管又は輸送のために弾性ストランドを包装するステップは、多くの方法で行うことができる。弾性ストランドのボビン又は弾性ストランドのボビンのペレットを、例えば適当な収縮包装により、障壁材料で包装する又は包むことができる。或いは、弾性ストランドのボビン又は弾性ストランドのボビンのペレットを、障壁材料からなる軟質プラスチックの袋に入れることもできる。すなわち、例えば水蒸気の侵入に対する抵抗性を有する軟質プラスチックの袋が裏打ちされた又は保持された、障壁材料を含む箱又はカートンに入れることができる。障壁材料を含む他の種類のコンテナを使用することもできる。弾性ストランドが、低湿度環境でありながら障壁材料を含むコンテナに入れられる場合は、コンテナ内部における弾性ストランド近傍の微視的環境は、この低湿度環境に対応するものとなる。コンテナ外部の湿度又は温度が調整されないような次の処理ステップを行うことができる。製造プロセスにおいて弾性ストランドが原料として使用されるまで、コンテナが開けられることはない。
【００６１】
弾性ストランドを包装するために、多くの方法を用いることができる。弾性ストランドを湿度制御又は温度制御された環境において第１巻取機で巻き付け、取り出し、包装するために湿度制御又は温度制御された環境に導くか又は運ぶことができる。或いは、弾性ストランドを第１巻取機において巻き付け、それからすぐに取り出し、包装するために湿度制御又は温度制御された環境に導くか又は運ぶことができる。
【００６２】
湿度制御又は温度制御された環境で、弾性ストランドのボビン又は弾性ストランドのボビンのペレットを、障壁材料を含むコンテナに入れる。水蒸気の侵入に対する抵抗性を有する好適な障壁材料は、これらに限定する意味ではないが、ポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリエステル、ポリカーボネート、ナイロン、セルロース、又はこれらの幾つかの組み合わせを含む。次いで、次の保管及び／又は輸送ステップの間に包装されたストランドに到達する可能性のある水蒸気の量を最小限にするような方法で、このコンテナを閉じる。例えば、障壁材料を含むコンテナが、軟質ポリエチレンの袋その他の軟質の水蒸気耐性のプラスチック袋である場合は、弾性ストランドのボビン又は弾性ストランドのボビンのペレットをこの袋に入れた後に、ヒートシールすることができる。或いは、弾性ストランドのボビン又は弾性ストランドのボビンのペレットを、ポリエチレン袋のような障壁材料が裏打ちされたカートン又は箱に入れ、弾性ストランドを入れた後にその袋をヒートシールすることもできる。
【００６３】
障壁材料を含むコンテナを閉じる前に、例えばヒートシールする前に、弾性ストランドの近くに乾燥剤を入れてもよい。コンテナが弾性ストランドの中に及び周りに水蒸気を侵入させるまで、この乾燥剤は、水蒸気を優先的に吸着又は吸収するように機能する。したがって、乾燥剤は、コンテナ内部の湿度を、強度の低下を最小限にする程度に維持するのを助ける。
有用な乾燥剤の例は、塩化カルシウム、硫酸カルシウム、シリカゲル、モレキュラーシーブ、Ａｌ_２Ｏ_３、又はこれらの幾つかの組み合わせを含む。乾燥剤は通常、水蒸気がその中に入って乾燥剤に接触することができ、乾燥剤を弾性ストランドから離れたまま保持することができる容器に入れられる。容器の例は、通常は主成分としてセルロースを含む天然繊維の繊維状ウェブ、或いは水蒸気を透過させるように形成されたポリエチレン又はポリプロピレン不織布のような不織材料からなるパウチである。
【００６４】
別の態様において、本発明はさらに、コンテナを閉じる前に、障壁材料を含むコンテナ内部において空気／水蒸気混合物を乾燥した不活性ガスで置換するステップを含む。例えば、弾性ストランドのボビンのペレットをコンテナ内部に入れた後に、軟質の導管を用いて、乾燥した窒素ガスをコンテナ内部に導くことができる。コンテナ内部から空気／水蒸気混合物が押し出されるのに十分な時間が経過した後に、コンテナから導管を取り外し、次いで該コンテナを閉じる。この置換ステップは、コンテナを閉じる前に、弾性ストランドと共に乾燥剤を入れるステップと組み合わせて行うこともできる。別の方法において、障壁材料を含むコンテナ内部の空気／水蒸気混合物が、該コンテナが閉じられる前に抜かれるように、包装システムを構成することができる。
【００６５】
別の態様において、障壁材料を含むコンテナを閉じる前に、弾性ストランドと共に湿度検出器が入れられる。弾性ストランドの購入者に輸送された後に袋又はコンテナを開ける時に、コンテナ内部の湿度が特定の値を超えていたかどうかを判断するためこの湿度検出器を調べることができる。湿度が特定の値を超えていた場合には、袋又はコンテナを受け取らずに仕入先に返品することができる。或いは、輸送品からサンプルを直ちに試験することもできる。ストランドの強度特性が条件を満たしているとみなされた場合には、輸送品を受理し、原料として使用することができる。好適な湿度検出器の一例は、コネチカット州スタンフォードのオメガ・エンジニアリング社から入手可能なカタログナンバーＨＣ‐１０／６０‐２００に対応する湿度計である。この湿度計は、１０パーセントから６０パーセントまでの範囲の相対湿度を検出することが可能である。
弾性ストランドと共に湿度検出器を入れるステップを、障壁材料を含むコンテナが閉じられる前にストランドと共に乾燥剤を入れるステップ、障壁材料を含むコンテナ内部の空気／水蒸気混合物を、該コンテナが閉じられる前に乾燥した不活性ガスで置換するステップ、又はこの両方のステップと組み合わせて行うことができる。
【００６６】
本発明の幾つかの実施形態において、弾性ストランドのボビンは、このストランドが製造された場所又はこのストランドが原料として使用される場所のいずれか或るいはこの両方で保管される。この保管ステップの間において、ストランドが包装されておらず、該ストランドが１０日よりも多く、特に２０日よりも多く、もっと特定すれば、３０日よりも多く保管され、その周囲湿度が、ストランドの強度を著しく低下させるようなものである場合は、該ストランドが保管される部屋、施設又は区域を、湿度制御又は温度制御された環境にすることもできる。しかし、前述のように、ストランドを押出し又は紡糸してからストランドを原料として使用するまでの全ての時間に関係なく、強度の低下を最小にするか又はなくすために、ストランドが押出し又は紡糸された後に、処理及び加工ステップの全てを湿度制御又は温度制御された環境で行うことができる。すなわち、障壁材料を含むコンテナ内部の「微視的環境」が低い水蒸気含有量（すなわち低湿度）を有するように弾性ストランドを包装し、これにより、包装の外部環境を制御する必要性がなくなり、後の処理ステップを行うことができるようになる。
【００６７】
本発明に従って加工又は処理された弾性ストランドを、多くの基体複合材と使い捨て吸収体物品に組み入れることができる。このような基体複合材及び／又は使い捨て吸収体物品の例は、本発明に関係する部分を引用によりここに組み入れる発明の名称「使い捨て失禁用衣類又はトレーニングパンツ」の米国特許第４，９４０，４６４号と、段落７の７行目から３４行目の収容フラップでの弾性ストランドの使用についての説明と、段落９の２９行目から段落１０の３６行目の弾性部材についての説明の部分を引用によりここに組み入れる発明の名称「弾性縁と収容システムを改良した吸収体物品」の米国特許第５，９０４，６７５号と、段落１１の３９行目から段落１２の２行目の弾性脚部部材についての説明の部分を引用によりここに組み入れる発明の名称「向上されたウエスト領域の乾燥性を有する吸収体物品とその製造方法」の米国特許第５，９０４，６７２号と、段落４の１８行目から４８行目の伸縮自在な脚部及びウエスト部材についての説明の部分を引用によりここに組み入れる発明の名称「集水溝を有する吸収体物品」の米国特許第５，９０２，２９７号に記載されている。本発明は、クリープ抵抗を向上させる（又は最終クリープを減少させる）ために熱処理された１つ又はそれ以上の弾性ストランドを組み入れた他の構造、複合体、又は製品に応用可能であり、強度の低下を抑えるために、水、又は水蒸気、或いはこの両方に対する露出が調整されるということを理解されたい。
【００６８】
本発明と共に使用することができるエラストマーのラミネートウェブ（すなわち、本発明の目的に係る弾性ストランドを組み入れた基体複合材）を作製する方法及び装置の例は、米国特許第５，９６４，９７３号の発明の名称「エラストマーのラミネートウェブを作製する方法及び装置」に見出され、前述のように本発明に関係する部分を引用によりここに組み入れる。この特許は、弾性ストランドを基体複合材の中に組み入れるための方法及び装置の例を与えるものであり、弾性ストランドとベース材料との間の接着の均一性及びその強度が向上するように熱処理された本発明の弾性ストランドを、基体複合材を形成するために他の方法及び装置で用いることもできる、ということについても理解されたい。
【００６９】
（実施例）
実施例１
ポリエステル‐ｂ‐ポリウレタンブロック共重合体からなる弾性ストランドのＧＬＯＳＰＡＮ８４０（Ｇｌｏｂｅ）ボビンを、グローブ・マニファクチャリング社から入手した。ＧＬＯＳＰＡＮ８４０のボビンは、半径３インチ、長さ１０インチのプラスチック芯を有するものであった。ＧＬＯＳＰＡＮ８４０弾性ストランドは、このストランドによって形成された外面がプラスチック芯の外面から半径方向外向きにおよそ３インチ延びるように、各プラスチック芯の周りに巻き付けられた。この特定の実験において、ストランドは、本発明者らがグローブ・マニファクチャリング社からボビンを入手する２週間以内に製造されたものであった。さらに、弾性ストランドは、シリコンベースの潤滑剤で被覆されていた。ボビンをプラスチック袋の中に入れて、密封した。ボビンの入った袋を、イリノイ州ブルムアイランド所在のブルー・エム社製の、型番ＯＶ‐４９０Ａ‐２の強制空気乾燥器に入れた。この乾燥器は、プラスチック袋を入れる前に、１０２℃の温度になるまで予め加熱された。この選択された温度に４時間曝した後に、ＧＬＯＳＰＡＮ８４０のボビンの入った袋を乾燥器から取り出した。
【００７０】
ボビンを乾燥器から取り出して、種々の基体複合材を作製するためにこのボビンを繰り出しスタンドの上に取り付けるまでに、およそ約２４時間経過した。基体複合材は、ジョージア州ドーソンビル所在のＪ＆Ｍラボラトリーズから入手可能な装置で作製された。ボビンの各々を、繰り出しスタンドの上に配置した。図４に示すように、ボビンからの個々のストランドを、直径４インチのゴムロール１１０と直径６インチのスチールロール１０４の２つのロールの間の、ニップ１０６に導いた。この場合は不織ウェブであるベース材料１０２を、対応する繰り出しスタンド（図示せず）からスチールロールの表面に導き、さらにニップを通り抜けるように導いた。第２不織ウェブ１０８を、その繰り出しスタンド（図示せず）からゴム・ロールの表面に導き、さらにニップを通り抜けるように導いた。この装置は通常、毎分１００フィートの速さで作動された。
【００７１】
この場合はＧＬＯＳＰＡＮ８４０であるエラストマーのストランド１００を、対応する繰り出しスタンド（図示せず）からコーム１１２を通して、弾性ストランドが２枚の不織ウェブの間に挟み込まれるように、さらにニップに導いた。コームは、ストランドの横方向の所望の分布を与え、それが維持されるように働く。ストランドは、この場合は不織ウェブであるベース材料の幅全体にわたって互いに約５ｍｍ離間するように配置された。
【００７２】
スチールロールとゴムロールの回転速度に対するストランド繰り出しスタンドの速度は、ストランドが、接着剤の塗布により不織ウェブに貼付けられた場合の約２００％に引き延ばされるような速度にされた。塗布した接着剤は、この場合はウィスコンシン州ウォーワトサ所在のアト・ファインドレイ社の英数字表示に基づいて入手可能なＨ‐２５２５Ａのホットメルト接着剤であった。接着剤は、４グラム毎平方メートル（すなわちｇｍ^−２）、７ｇｍ^−２、及び１０ｇｍ^−２の３つの異なる塗布量で塗布された。これら３つの塗布量の各々に関して、接着剤は、スワール塗布法又はメルトブロー塗布法の、２つの空気堆積技術のうちのいずれか１つを用いて塗布された。
【００７３】
接着剤を取り付けるのに使用したアプリケータ１１４は、塗布量や空気堆積技術の使用とは関係なく、接着剤が最初に塗布されるウェブの表面にほぼ平行な図示したノズル前面が、ウェブの表面から１．５インチ１１６の位置になるように配置された。さらに、接着剤が最初に塗布されるウェブに垂直な図示したノズルの中心軸線は、ゴムロールとスチールロールにより形成されたニップを通る平行軸線から８インチ１１８の位置であった。
【００７４】
表１は、多くの基体複合材についての、次の変数、すなわち（１）Ｈ‐２５２５Ａ接着剤を塗布するのに用いた空気堆積技術（スワール塗布法又はメルトブロー塗布法）、（２）Ｈ‐２５２５Ａ接着剤の塗布量（４ｇｍ^−２、７ｇｍ^−２、又は１０ｇｍ^−２）、（３）（１平方ヤード当たり０．５オンスの坪量を有し、ポリプロピレン繊維からなり、２つのベース材料として働く２枚のスパンボンドウェブ、又はスパンボンド‐メルトブロー‐スパンボンド材料からなり、ラミネート全体が１平方ヤード当たり約０．６オンスの坪量を有し、その３つの層の各々が、ポリプロピレン繊維からなるスパンボンドか又はメルトブローのラミネートである、３層ラミネートの２つのベース材料の）間に弾性ストランドが挟み込まれたベース材料の種類、及び（４）基体複合材を形成するためストランドをベース材料に付着する前に、弾性ストランドが前述の手順を用いて加熱されたかどうか、の関数として最終クリープを測定した多数の実験の結果を示すものである。
【００７５】
結果（表１参照）は、本発明に係る加熱されたＧＬＯＳＰＡＮ８４０は、最終クリープを減少させる、すなわちクリープ抵抗を向上させるということを示す。さらに、弾性体の加熱により、与えられた最終クリープ値を得るのに必要とされる接着剤の量を減らすことができる。例えば、メルトブロー塗布技術を用いてＨ‐２５２５Ａ接着剤を７ｇｍ^−２の塗布量で塗布した場合、熱処理され２枚のスパンボンドウェブの間に挟み込まれたＧＬＯＳＰＡＮ８４０弾性ストランドについて、２２．９％の最終クリープ値が得られた。しかしながら、熱処理されていないＧＬＯＳＰＡＮ８４０を組み入れた対照用基体複合材は、同じ２２．９％の最終クリープ値を得るために、１０ｇｍ^−２のＨ‐２５２５Ａ接着剤塗布量を必要とした。
【００７６】
表１

【００７７】
実施例２
ポリエーテル‐ｂ‐ポリウレタンブロック共重合体からなる弾性ストランドのＬＹＣＲＡ９４０ボビンを、デラウェア州ウィルミントン所在のデュポン社から入手した。ＬＹＣＲＡ９４０のボビンは、半径３インチ、長さ４インチのプラスチック芯を有するものであった。ＬＹＣＲＡ９４０弾性ストランドは、このストランドによって形成された外面がプラスチック芯の外面から半径方向外向きにおよそ３インチ延びるように、各プラスチック芯の周りに巻き付けられていた。この特定の実験において、ストランドは、本発明者らがデュポン社からボビンを入手する２週間以内に製造されたものであった。各ボビンを、イリノイ州ブルムアイランド所在のブルー・エム社製の、型番ＯＶ‐４９０Ａ‐２の強制空気乾燥器に入れた。この乾燥器は、ボビンを乾燥器に入れる前に、１０２℃の温度になるまで予め加熱された。この選択された温度に４時間曝した後に、ＬＹＣＲＡ９４０のボビンを乾燥器から取り出した。
【００７８】
ボビンを乾燥器から取り出して、種々の基体複合材を作製するためこのボビンを繰り出しスタンドの上に取り付けるまでに、およそ約２４時間経過した。基体複合材は、ジョージア州ドーソンビル所在のＪ＆Ｍラボラトリーズから入手可能な装置で作製した。ボビンの各々を、繰り出しスタンドの上に配置した。図４に示すように（図面番号が特定された装置の部分と対応している前の実施例を参照する）、ボビンからの個々のストランドを、直径４インチのゴムロールと直径６インチのスチールロールの、２つのロールの間のニップに導いた。この場合は不織ウェブであるベース材料を、対応する繰り出しスタンド（図示せず）からスチールロールの表面に導き、さらにニップを通り抜けるように導いた。第２不織ウェブを、その繰り出しスタンド（図示せず）からゴム・ロールの表面に導き、さらにニップを通り抜けるように導いた。この装置は通常、毎分１００フィートの速さで作動された。
【００７９】
この場合はＬＹＣＲＡ９４０であるエラストマーのストランドを、対応する繰り出しスタンド（図示せず）からコームを通して弾性ストランドが２枚の不織ウェブの間に挟み込まれるようにニップに導いた。コームは、ストランドの横方向の所望の分布を与え、それを維持するように働く。ストランドは、この場合は不織ウェブであるベース材料の幅全体にわたって互いに約５ｍｍ離間するように配置された。
【００８０】
スチールロールとゴムロールの回転速度に対するストランド繰り出しスタンドの速度は、ストランドが、接着剤の塗布により不織ウェブに貼付けられた場合の約２００％に引き延ばされるような速度にされた。塗布した接着剤は、この場合はウィスコンシン州ウォーワトサ所在のアト・ファインドレイ社の英数字表示に基づいて入手可能なＨ‐２５２５Ａのホットメルト接着剤であった。接着剤は、４グラム毎平方メートル（すなわちｇｍ^−２）、７ｇｍ^−２、及び１０ｇｍ^−２の３つの異なる塗布量で塗布された。これら３つの塗布量の各々に関して、接着剤は、スワール塗布法又はメルトブロー塗布法の、２つの空気堆積技術のうちのいずれか１つを用いて塗布された。
【００８１】
接着剤を取り付けるのに使用したアプリケータは、塗布量や空気堆積技術の使用とは関係なく、接着剤が最初に塗布されるウェブの表面にほぼ平行な図示したノズル前面が、ウェブの表面から１．５インチの位置になるように配置された。さらに、接着剤が最初に塗布されるウェブに垂直な図示したノズルの中心軸線は、ゴムロールとスチールロールにより形成されたニップを通る平行軸線から８インチの位置であった。
【００８２】
表２は、多くの基体複合材についての、次の変数、すなわち（１）Ｈ‐２５２５Ａ接着剤を塗布するのに用いた空気堆積技術（スワール塗布法又はメルトブロー塗布法）、（２）Ｈ‐２５２５Ａ接着剤の塗布量（４ｇｍ^−２、７ｇｍ^−２、又は１０ｇｍ^−２）、（３）（１平方ヤード当たり０．５オンスの坪量を有し、ポリプロピレン繊維からなり、２つのベース材料として働く２枚のスパンボンドウェブ、又はスパンボンド‐メルトブロー‐スパンボンド材料からなり、ラミネート全体が１平方ヤード当たり約０．６オンスの坪量を有し、その３つの層の各々が、ポリプロピレン繊維からなるスパンボンドか又はメルトブローのラミネートである、３層ラミネートの２つのベース材料の）間に弾性ストランドが挟み込まれたベース材料の種類、及び（４）基体複合材を形成するためストランドをベース材料に付着する前に、弾性ストランドが前述の手順を用いて加熱されたかどうか、の関数として最終クリープを測定した多数の実験の結果を示すものである。
【００８３】
この結果は、本発明に係る加熱されたＬＹＣＲＡ９４０が、最終クリープを減少させる、すなわちクリープ抵抗を向上させるということを示す。さらに、弾性体の加熱により、与えられた最終クリープ値を得るのに必要とされる接着剤の量を減らすことができる。例えば、スワール塗布技術を用いてＨ‐２５２５Ａ接着剤を４ｇｍ^−２の塗布量で塗布した場合、熱処理され２枚のスパンボンドウェブの間に挟み込まれたＬＹＣＲＡ９４０弾性ストランドについて、４６．３％の最終クリープ値が得られた。しかしながら、熱処理されていないＬＹＣＲＡ９４０を組み入れた対照用基体複合材は、同じ４６．３％の最終クリープ値を得るために、７ｇｍ^−２のＨ‐２５２５Ａ接着剤塗布量を必要とした。
【００８４】
表２

【００８５】
実施例３
熱重量分析と示差走査熱量測定法を用いて、ＧＬＯＳＰＡＮ８４０のサンプルの熱安定度を測定した。熱重量分析において、ＧＬＯＳＰＡＮ８４０のサンプルを、デラウェア州ニューキャスル所在のＴＡインストルメンツ社製の、熱重量分析器モデル９５１の加熱エレメントの中のサンプルホルダに入れた。このサンプルを、約２１℃の室温から４５０℃の温度まで、毎分１０℃の加熱速度で加熱した。このサンプルは、毎分およそ８０ミリメートルの空気流により、空気の動的雰囲気の下で加熱された。どんな重量の減少をも検出できるように、加熱の間にるつぼを継続的に秤量した。結果として得られた重量変化曲線すなわちサンプル重量対温度のプロットは、ＧＬＯＳＰＡＮ８４０の分解温度が空気中において約２４０℃であったということを示した。
【００８６】
示差走査熱量測定法を用いる分析において、１０ミリグラムのＧＬＯＳＰＡＮ８４０のサンプルを、ＴＡインストルメンツ社製の示差走査熱量測定器モデル２９２０の、加熱／冷却ブロックのサンプルチャンバの中に入れた。このサンプルを、毎分１０℃の加熱及び冷却速度で、−１００℃から２００℃まで加熱し、次いで−１００℃まで冷却し、２００℃まで再加熱した。この示差走査熱量測定器モデル２９２０に、同じくＴＡインストルメンツ社製の液体窒素冷却用の付属品を取り付けた。この結果は、約２０℃から約２００℃までの温度範囲において、エネルギー吸収または放出を示す大きなピークは無かったことを示した。したがって、ＧＬＯＳＰＡＮ８４０は、この温度範囲において酸化及び熱に対して安定であると思われる。
【００８７】
実施例４
ポリエステル‐ｂ‐ポリウレタンブロック共重合体からなる弾性ストランドのＧＬＯＳＰＡＮ８４０（Ｇｌｏｂｅ）ボビンを、グローブ・マニファクチャリング社から入手した。この弾性ストランドは、シリコンベースの潤滑剤で被覆されていた。このストランドのサンプルを、温度が華氏１００度の値まで制御され、相対湿度が８０％の値まで制御されている制御された環境に置いた。これらの条件に対する露出の選択された時刻において、ストランドのサンプルを制御された環境から取り出し、試験室に移した。サンプルを制御された環境から取り出して該サンプルを試験するまでに、およそ約１５分から３０分の時間が費された。
【００８８】
ミネソタ州エデン・プレイリー所在のＭＴＳシステム・コーポレーションから入手可能なシンテック引張試験機を用いて、ストランドのサンプルの引張り強さと伸長の両方を測定した。引張試験機の対向するホルダは、円筒形のロッドからなるものであった。標点距離は、ロッド中心軸間の距離が１．５インチになるようにホルダを移動させることにより、１．５インチに設定された。次いで、ストランドの長さの一端を、一方の円筒形ロッドの周りに２回巻き付けた。次いで、もう一方の端を取り出し、もう一方の円筒形ロッドの周りに２回巻き付けた。次いで、対向するホルダが毎分２０±０．４インチのクロスヘッド速度で反対方向に移動するように、試験機を作動させた。ストランドは、破損するまでこの速度で引き伸ばされた。ストランドが破損した位置で、単位長さ当たりの長さの変化を反映する、ピーク負荷値（グラム）と伸長（パーセント）を記録した。この試験プロセスでは、相対湿度と温度が特定された条件での露出が選択された回数繰り返され、次のような引張り強度（すなわちピーク負荷値）が得られた（各値は、５回から１０回までの繰返しの平均を反映するものである）。温度華氏１００度、相対湿度８０％に曝される前のストランドのピーク負荷値は、約３７５グラム（伸長度は約１０８０％）であり、およそ５日間この特定の条件に曝された後のピーク負荷値は、約３４５グラムまで減少し（伸長度は約１１７５％）、およそ１８日間、この特定の条件に曝された後のピーク負荷値は、約２５０グラムまで減少し（伸長度は約１２００％）、およそ３０日間、この特定の条件に曝された後のピーク負荷値は、約２４５グラムまで減少し（伸長度は約１１４５％）、およそ６５日間、この特定の条件に曝された後のピーク負荷値は、約１５０グラムまで減少した（伸長度は約８７０％）。このデータは、水蒸気により弾性ストランドの強度が低下することを示す。
【００８９】
実施例５
実施例１に記載されたＧＬＯＳＰＡＮ８４０のボビンと同じサンプルを、温度が華氏１２０度、相対湿度が２０％に制御された環境に置いた。実施例１で説明したのと同じ手順を用いて、このストランドのサンプルについてのこの条件に対する露出を選択された回数試験し、次のような結果が得られた（各値は、５回から１０回までの繰返しの平均を反映するものである）。温度華氏１２０度、相対湿度２０％に曝される前のストランドのピーク負荷値は、約３７５グラム（伸長度は約１０８０％）であり、およそ５０時間この特定の条件に曝された後のピーク負荷値は、約４００グラム（伸長度は約１１２５％）であり、およそ１８０時間この特定の条件に曝された後のピーク負荷値は、約４５５グラム（伸長度は約１２５０％）であり、およそ５００時間この特定の条件に曝された後のピーク負荷値は、約４１０グラム（伸長度は約１２７５％）であった。このデータは、水蒸気に対する弾性ストランドの露出を調整することで、ストランド上での水の作用に起因する強度の低下量が抑えられることを示す。
【００９０】
本発明は、特定の形態についてかなり詳細に説明されてきたが、他の変形も可能である。付属の請求項の精神及びその範囲は、ここに記載された特定の形態に限定されるものではない。
【図面の簡単な説明】
【図１】
弾性ストランドを作製するための装置の１つの断面図である。
【図２】
弾性ストランドを作製するための装置の１つの断面図である。
【図３】
クリープ試験による変化が与えられたときの基体複合材の状態を順次に示す図である。
【図４】
１つ又はそれ以上の弾性ストランドを少なくとも１つのベース材料に取り付けるためのプロセスの１つの側面図である。[0001]
(Background technology)
People rely on disposable absorbent articles to participate in everyday activities and have fun.
Disposable absorbent articles, including adult incontinence articles and diapers, are generally manufactured by laminating several components. These components typically include a liquid-permeable topsheet, a liquid-impermeable backsheet attached to the topsheet, and an absorbent core disposed between the topsheet and the backsheet. Including. When the disposable article is worn, the liquid-permeable topsheet is located right next to the wearer's body. The topsheet allows bodily fluids to move into the absorbent core. The liquid impermeable backsheet helps to prevent body fluids retained in the absorbent core from leaking. The absorbent core is designed to have desirable physical properties, such as a high absorption capacity and a high absorption rate, so that bodily fluids can be transferred from the wearer's skin into the disposable absorbent article.
[0002]
Some disposable absorbent articles are formed with various types of stretchable waistbands and stretchable leg bands or cuffs. One way to create a stretchable zone is to incorporate elastic strands into a disposable absorbent product. For example, elastic strands have been laminated between polymer film layers and / or woven or nonwoven layers to form such areas. Fold layers have also been used to enclose or enclose selected strand materials. These folded layers have been used to confine elastomeric strands within the waistband, leg cuff, and inner barrier cuff components of disposable diapers and other disposable absorbent articles. The one or more polymer films, woven or nonwoven layers, and / or fold layers can be an integral part of the topsheet and / or backsheet, or the topsheet and / or backsheet. It can be another component to be adhered to.
[0003]
In order to introduce elastic strands into the product being manufactured, usually a spool of strand is placed on a payout stand. Next, the strands are continuously unwound in the longitudinal direction in a state where the strands are attached to a support such as a base material layer to form a base composite material. As noted above, examples of base materials include, but are not limited to, polymer films and / or woven or non-woven fabrics. Also, as described above, the elastic strands are typically sandwiched between two different base material layers or between folded portions of the base material to form a base composite. The strands are often bonded to one or more base materials using an adhesive.
[0004]
To form the stretchable zone, the strands are elastically stretched as the strands are bonded to the base material to form a base composite. The stretched elastic strands tend to shrink and gather into the substrate composite, which imparts elastomeric properties to the substrate composite. As described above, the base composite can be formed to include a stretchable waistband or leg band of the disposable absorbent article.
[0005]
In a substrate composite, if one or more elastic strands are not uniformly adhered to one or more base materials with sufficient strength, the stretchable region can provide the desired elastomeric properties. In the case of a disposable absorbent article, a desired fit cannot be given to a wearer.
One way to improve the uniformity and strength of the bond is to increase the amount of adhesive used to bond the elastic strand to one or more base materials. This approach is not always desirable in terms of adhesive costs.
[0006]
What is needed is a substrate composite that incorporates one or more elastic strands more uniformly and / or firmly adhered to one or more base materials, and such substrate composites Is a manufacturing method.
[0007]
(Disclosure of the Invention)
The inventors have stated that the uniformity and / or strength of the bond between one or more elastic strands and one or more base materials in the substrate composite is improved by heating the strands. I found something. By heating one or more elastic strands prior to bonding, the creep resistance, which is a measure of the uniformity and strength of the bond between the elastic strands and the base material, is about 5% or more, especially about Increase by 10% or more, more specifically about 15% or more. Accordingly, the present invention is directed to improving the uniformity and / or strength of the bond between the elastic strand and the base material by heating the strand prior to bonding. The strands can be heated by heat conduction and / or convection, or by radiative methods incorporating, for example, infrared or microwave radiation, or some combination thereof. If the elastic strand is manufactured at a different location than where the strand is used as a raw material, the strand may be heated at either location. Further, the strands may be heated in-line, ie, as part of a strand manufacturing process or a process using strands as a raw material, or may be heated off-line, ie, in a step different from any of the foregoing.
[0008]
One method that includes the features of the present invention is to provide an elastic strand, heat the strand, position the strand such that the strand is located between the first base material and the second base material, An adhesive is applied to the strand, the first base material, the second base material, or some combination thereof, such that at least a portion is adhered to at least a portion of the first base material and at least a portion of the second base material. And heating the strands to compare the creep resistance of the substrate composite with the creep resistance of the substrate composite formed in the same manner using the same material except that the strands are not heated. About 5% or more, especially about 10% or more, more particularly about 15% or more.
In some variations of the invention, the first base material and the second base material are the same material, and the strands are disposed between the folds of the material and adhered to one or both of its inner surfaces. .
[0009]
In some exemplary embodiments of the invention, the elastic strands are polyester, polyurethane, polyether, polyamide, polyacrylate, polyester-b-polyurethane block copolymer, polyether-b-polyurethane block copolymer, Or a polyether-b-polyamide block copolymer. In another aspect, the strand is coated with a lubricant.
[0010]
Some methods of the present invention include heating the strand by directing hot air, infrared radiation, or microwave radiation onto the strand.
In one embodiment, the strand is heated by placing the bobbin of the strand in a heated environment at an air temperature between 100 ° C and 200 ° C for 2 or more hours, especially about 4 hours or more. .
[0011]
One method that includes the features of the present invention involves preparing an elastic strand consisting of a polyester-b-polyurethane block copolymer or a polyether-b-polyurethane block copolymer, wherein the strand comprises a surface of the strand. Before the strands are bonded to the base material, the strands are heated by a heating step that includes exposing the strands to hot air, infrared radiation, microwave radiation, or a combination thereof, so that the strands are bonded to the first base material. Disposing the strands so as to be located between the second base material and the strands such that at least a portion of the strands is adhered to at least a portion of the first base material and at least a portion of the second base material. At least about 4 grams per first base material, second base material, or some combination thereof; The creep resistance value of a substrate composite comprising a heat-treated elastic strand prepared by a step comprising applying an adhesive at a laydown of greater than or equal to It is at least about 5% greater than the creep resistance of the composite.
[0012]
In another embodiment of the present invention, the elastic strand is provided with an elastic strand produced by a step consisting of extrusion, spinning or other method of producing the strand, heating the elastic strand and applying the claimed priority of the present application. No. 60 / 166,348, filed Nov. 19, 1999 (KC Internal Invention Disclosure No. 15427), filed Nov. 19, 1999, which is hereby incorporated by reference, and which is incorporated herein by reference. As described in the title of the invention, "Method for suppressing strength deterioration of elastic strands", a substrate incorporating a heat-treated elastic strand by adjusting the exposure of the strand to water or water vapor before, during, or after heating. The composite is at least about 5% less than the creep resistance of the base composite incorporating the unheated elastic strands, Treated by a step comprising bonding the heat treated elastic strand to at least one base material to form a substrate composite having a creep resistance value that is about 10%, more specifically about 15% greater. You.
[0013]
Examples of various methods of adjusting the exposure of the elastic strand to water or water vapor that can be used before, during, or after heating the elastic strand are described below.
[0014]
In some embodiments, during manufacture of the strand, during storage of the strand at the geographic location where the elastic strand was manufactured, geography where the elastic strand will be used as a raw material from the geographic location where the elastic strand was manufactured. During the transport of the strand to a target location, during storage of the strand in a geographical location where the elastic strand will be used as raw material, during use of the elastic strand as raw material, or during some combination of these. Before heating, the specific humidity around the heating should be such that the water vapor per pound of dry air does not exceed about 0.01 pounds of steam, especially the water vapor per pound of dry air does not exceed about 0.005 pounds. During or after heating the exposure of the elastic strands to water vapor is adjusted. In one aspect, the elastic strand is used as a raw material to produce a base composite comprising the elastic strand or an absorbent article comprising the elastic strand.
In another aspect, the exposure of the elastic strands to water vapor is regulated during transport of the elastic strands from the geographical location where the elastic strands were manufactured to the geographical location where the elastic strands are used as a feedstock.
[0015]
In some exemplary embodiments, adjusting the exposure of the strand to water vapor comprises controlling the temperature around the strand or around the container containing the strand. For example, the temperature can be controlled to a value that does not exceed about 55 degrees Fahrenheit. By adjusting the temperature, the maximum humidity obtained is adjusted (i.e., as the temperature of the air decreases, the ability of the air to retain water vapor decreases).
In another variation of the invention, adjusting the exposure of the strands to water vapor includes controlling the humidity around the strands or around the container containing the strands.
[0016]
In another variation of the invention, adjusting the exposure of the elastic strands to water vapor includes placing the strands in a container containing the barrier material before or after heating the strands and closing the container.
In another aspect, the container containing the barrier material is transported after the strand is first manufactured and when the strand is transported from the geographic location where the strand was first manufactured to the geographic location where the strand is used. Time t, which is earlier than time₁Closed at
In yet another aspect, the specific humidity around the strand is at time t₁And a time t, which is the time when the closed container having the barrier material is first opened.₂In between, the water vapor per pound of dry air is such that it does not exceed about 0.017 pounds, in particular about 0.01 pounds, more particularly about 0.005 pounds.
[0017]
In some variations of the invention, the barrier material comprises polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyester, polycarbonate, nylon, cellulose, or a combination thereof.
In another aspect, closing the container containing the barrier material includes heat sealing the container, the barrier material, or both.
Some exemplary embodiments include placing a desiccant with the strands before heat sealing the container, barrier material, or both. Possible desiccants include calcium chloride, calcium sulfate, silica gel, molecular sieve, Al₂O₃Or some combination of these.
Another variation of the present invention is to replace the air and water vapor mixture inside the container containing the barrier material with a dry inert gas prior to heat sealing the container, the barrier material, or both, the container, the barrier material. Or placing the hygrometer inside the container containing the barrier material before heat sealing both, or both.
[0018]
The present invention includes an elastic strand that is heated to increase the creep resistance of the substrate composite, the substrate composite, and / or a disposable absorbent product that includes the strand. Further, as described above, the elastic strands can also be handled such that the exposure of the strands to water or water vapor is adjusted before, during, or after heat treatment of the strands.
[0019]
These and other features, aspects, and advantages of the present invention will be better understood from the following detailed description, the appended claims, and the accompanying drawings.
[0020]
(Best Mode for Carrying Out the Invention)
The present invention is directed to improving the adhesion between an elastic strand and a base material in a substrate composite. Generally, the method of the present invention involves heating the strand with heated air, some type of radiation, such as microwave or infrared radiation, or some combination thereof. If the strand is manufactured in a location different from the location where it is used as a raw material, the elastic strand may be heated at its manufacturing location and / or where it is used as a raw material or at both locations. It may be heated. Further, the strands can be heated as part of either an in-line or strand manufacturing process or a process where the strands are used as a feedstock, or off-line or in a separate step from any of these processes. One method that includes the features of the present invention is to provide an elastic strand produced by steps including extrusion, spinning, or other methods of producing the strand, heat the strand, and incorporate the heated elastic strand. The substrate composite has a creep resistance value that is at least about 5%, more specifically about 10%, and more specifically about 15% greater than the creep resistance value of the substrate composite incorporating the unheated elastic strand. Attaching a strand to at least one base material to form a substrate composite to have. These other embodiments of the present invention, including those directed to substrate composites and disposable absorbent products, are described in more detail in the following paragraphs.
[0021]
Elastic strands can be made in a variety of ways, including, but not limited to, extrusion and spinning. In the extrusion process shown in FIG. 1, polymer chips, fine particles, pellets, and other solids 10 are put into a hopper 12. The solid polymer is led from the hopper into the chamber 14. The polymer is continuously propelled through the chamber by a rotating screw 16. As the polymer travels through the chamber, its temperature and pressure are such that the solid polymer melts and hardens. Although some heat is generated by friction, an external heat source 18 is also typically used to heat the polymer. The molten polymer is then extruded from the die 20 to obtain strands, continuous fibers, or filaments of the desired structural shape. Possible cross-sectional shapes include, but are not limited to, a circle, a shape having three protrusions, a polyhedron, a rectangle (eg, a ribbon) or an ellipse. The strand cools and solidifies after exiting the extruder.
[0022]
Without using a polymer as a feed, one or more monomers in the form of chips, microparticles, pellets, or other solid form can also be added to the extruder. Alternatively, a prepolymer having a molecular weight greater than the monomer molecular weight and less than the final polymer molecular weight can be added to the extruder. Monomers or prepolymers can be added with compounds that promote polymerization. The polymerization occurs in the chamber of the extruder, but may or may not be completed before the material exits the die. If the polymerization is not completed, some polymerization may occur after the material has been extruded. Also, some of the monomers or prepolymers may react and not ultimately become part of the polymer chains of the strand.
[0023]
Polyester-b-polyurethane block copolymers, including, but not limited to polyesters, polyurethanes, polyethers, polyamides, polyacrylates, or combinations thereof, and / or polyether-b-polyurethane block copolymers, and / or Alternatively, many materials can be extruded, including block, random, or graft copolymers, such as polyether-b-polyamide block copolymers, to obtain elastic strands. As mentioned above, a monomer or prepolymer precursor may be added to the extruder to obtain a polymeric material of the type described above.
[0024]
The present invention may be used with the subject matter disclosed in co-pending US patent application Ser. No. 60 / 166,348. If the elastic strand is susceptible to the action of water (eg, hydrolysis), the reduction in strand strength due to the action of water can be controlled by adjusting the exposure of the strand to water or water vapor. . If the elastic strands are manufactured, stored, transported or otherwise treated in such a way that the strength of the strands is significantly reduced by the action of water or steam, the heat treatment of the strands according to the invention is In addition, improving creep resistance (ie, improving the uniformity and strength of the bond between the elastic strands and the base material in the base composite) may be ineffective. As described below, the exposure of the strands to water or water vapor is adjusted before heating the strands, during heating the strands, after heating the strands, or at some combination of these.
[0025]
In producing the elastic strand, a crosslinking agent may be used. After the material is extruded, a crosslinking reaction occurs until the polymer chains are crosslinked. This may be done in a separate processing step, for example, after the strand has been extruded.
[0026]
After the strand exits the extruder, another processing step can be performed. These processing steps can be performed anywhere between the position where the strand is extruded and the position where the strand is first wound on a bobbin, spindle or spool. Alternatively, one or more of these processing steps can be performed after the strand has been first wound. After the elastic strand bobbin is made, it is later unwound and processed in some manner before being re-wound.
[0027]
Other processing steps include, but are not limited to: Air can be directed to the strands exiting the die to increase the cooling rate. A scouring step can be included to remove impurities from the strand by exposing the strand to soap or detergent. Lubricants can be applied to the strands to reduce friction between the strands or between the strands and the components of the device. Possible lubricants include, but are not limited to, vegetable or mineral oils, suitably refined petroleum products, silicon-based materials, or surfactants. Also, a stretching step can be included to stretch the polymer to provide the desired physical properties. In one example of another stretching step, the strand is guided over two sets of rolls. The strands pass over a first set of rolls moving at a first speed and then over a second set of rolls moving at a second speed higher than the first speed. The difference in speed between the first set of rolls and the second set of rolls increases the tension in the strands, thereby causing the constituent polymers of the strands to stretch and provide other changes that alter the physical properties of the strands. help.
After these other additional processing steps, the strand is wound for storage or transport to another geographic location. During this other step, where the spool, reel or bobbin of elastic strands is unwound and then wound, the strands can be treated with various additives such as detergents, surfactants, or dyes. .
[0028]
Various spinning processes can be used to form elastic strands or fibers, in addition to the examples from the extrusion process described above. Generally, these processes require dissolving or melting the polymer in solution.
In a melt spinning process as shown in FIG. 2, polymer chips, microparticles, pellets, and other solids 30 are heated by a heated metal grid 32 and other heating devices. The resulting molten polymer 34 is delivered under high pressure conditions through a plate called a spinneret 38. A plurality of small holes are formed in the plate as a whole. The molten polymer solidifies from the front of the spinneret, usually flowing into the air. These multiple strands 40 are bundled to form a cable-like or rope-like structure composed of a plurality of strands.
[0029]
The polymer is typically melted by contacting a hot grid in the form of a steel tube that is electrically heated by some other means. The spinning pump 36 or a combination of spinning pump and booster pump can be used to direct the molten polymer to and through the spinneret. Alternatively, an extrusion-type screw can be used to assist in melting the polymer and adjust the amount of the resulting polymer that reaches and passes through the spinneret.
[0030]
Generally, the strands or filaments flow out of the front of the spinneret into the air and begin to cool. Air jets or blast air directed at the outgoing strands can be used to speed up the cooling process. After the strands or filaments have traveled enough to set, they are further processed. As noted above, additional processing steps include, but are not limited to, scouring, lubricating, or stretching one or more strands. FIG. 2 shows a lubrication disk and trough 42 for applying a lubricant to one or more strands, for example. After the processing is completed, the strand (in this case, a cable-like or rope-like structure) is wound around a reel, a spindle, a spool, or a bobbin 44 at a winding place. Before being wound, the strands may pass over one or more rolls 46.
[0031]
Other spinning processes include wet spinning, in which a solution of a polymer or polymer derivative is drained from a spinneret into a liquid that solidifies the polymer or polymer derivative to form a strand, and a solution of the polymer is transferred from the spinneret to air or solvent. Comprises dry spinning, which drains into an evaporating inert gas atmosphere, thereby forming filaments or strands. An example of such a method is described in Fred W. et al. Billmeyer, Jr. , "Textbook of Polymer Science" (Wiley Interscience, 2nd edition, 1971), pp. 518-530.
[0032]
Generally, the same polymeric, prepolymer, or monomer materials that are useful for extruding elastic strands are also useful for spinning elastic strands. Examples of such materials are described above. Further, a crosslinking agent can be used. Similarly, cross-linking occurs after the strand or filament exits the spinneret.
It should be understood that the above provides an example of a method of making an elastic strand. The invention is not limited to these examples and can be used in combination with other processes for producing elastic strands.
[0033]
Before citing data indicating that heating the elastic strands increases the creep resistance of the substrate composite incorporating the heated strands, it is useful to explain certain terms. "Creep resistance" or "creep resistance" for the purposes of the present invention refers to the elastic strand retention of a particular system, which allows one or more elastic strands to be attached to at least one base material. For example, if the adhesive is applied in liquid form to a base material and then one or more elastic strands are pressed against the adhesive to attach the one or more elastic strands to the base material, the creep resistance Is a measure of the quality of the adhesive bond between one or more strands and the base material.
[0034]
The description of the creep measurement test gives another detail on this concept. As described next, the substrate composite was formed by sandwiching a plurality of elastic strands between two base materials to form a substrate composite or laminate support. As shown in FIG. 3, a 60 millimeter wide and 250 millimeter long sample 60 was cut from a continuous web of substrate composite. The substrate composite incorporated ten elastic strands 62 (all strands not shown) positioned approximately 5 mm apart from each other across the width of the substrate composite. To perform the creep measurement test, the sample was first fully stretched by hanging it vertically in front of a lit light box. The top of the sample was clamped to the light box, and a 1000 gram weight was clamped to the bottom of the sample (arrow 64 indicates the effect of the weight). In this fully stretched configuration, a template was used to mark 200 millimeters in length near both ends of the support (sample material over 200 mm in length is not shown).
[0035]
The weight was then removed and the sample was laid horizontally on a piece of cardboard. The substrate composite 68 was shrunk so that the distance between the marks on the substrate composite was 175 millimeters 70 (similarly, sample material over 175 mm in length is not shown). The sample was then stapled to cardboard with staples (not shown) placed outside a 175 mm long location. Except for the outermost line representing the edge of the substrate composite, this partially contracted shape, ie, a line parallel to the length dimension of the sample of 175 mm, represents the elastic strand 62 (all strands not shown). . Lines perpendicular to the length of the substrate composite (except for the outermost line perpendicular to the length, which also indicates that the distance between the indicia on the substrate composite is 175 mm) FIG. 9 represents the gathering of the base material caused by the elastomeric strands shrinking after the weight has been removed. As the elastic strands shrink, they gather into the base material, such that the base composite itself has elastomeric properties.
[0036]
The elastic strand was then cut off at marks 72 and 74 representing a length of 175 mm. Since the strands were located between two base materials, typically one of the base materials was partially or completely slit when the strands were cut. After cutting off the elastic strands 62, the elastic strands shrank entirely. About 1 to 2 minutes after cutting the strand, the length of the contracted strand was measured. 175 mm and the initial contracted strand length 78, ie I_initialThe "initial creep" of the sample was calculated using the difference from. In the present invention, the initial creep is calculated using the following equation.

After determining the initial creep of the sample, the substrate composite 76 (stapled to cardboard) was placed in a preheated forced air dryer to a temperature of 100 degrees Fahrenheit. After 90 minutes, the substrate composite and cardboard were removed from the dryer. The substrate composite was then allowed to cool for approximately 10 minutes. Here, the length of the further contracted strand was measured.
175 mm and the length 78 of the last contracted strand, that is, Y_finalThe "final creep" of the sample was calculated using the difference from. In the present invention, the final creep is calculated using the following equation.

ク リ ー The creep resistance or creep resistance value according to the object of the present invention is calculated as follows.
Creep resistance,% = 100−final creep [Equation 3]
[0037]
In a disposable absorbent article worn near the wearer's body, the final creep provides a measure of the article's performance during use, as human body temperature is about 98 degrees Fahrenheit. The hypothetical situation gives details about the significance of this measurement. Suppose that a base composite is made with three elastic strands sandwiched between two base materials or one folded base material. It is also assumed that attaching the strands to the base material using an adhesive creates a laminate in which the strands have an elongated shape, typically about 200% to about 300% elongation (see next example). United States of America, entitled "Method and Apparatus for Making Elastomeric Laminate Webs," which incorporates by reference portions of the present invention, for details of how to make a substrate composite incorporating elastic strands. Patent No. 5,964,973). If after aging at 100 degrees Fahrenheit for 90 minutes, the elastic strands are stripped from the adhesive and base material adhering to most of the length of each strand and the strands shrink, the final creep is relatively high and the creep The resistance will be relatively low. The peel strength of the peeled strands is small, and the gathers that fall on one or more base materials in a relatively uniform finish along the length of the substrate composite are small, so that the elastomer composites The performance of the substrate composite is reduced.
[0038]
In the second hypothetical situation, again assume that the substrate composite is made as described in the previous paragraph. Also assume that the strands are attached to one or more base materials using an adhesive. If the elastic strands remain uniformly attached to the base material along most of the length of each strand after aging at 100 degrees Fahrenheit for 90 minutes, the final creep is relatively low and the creep resistance is comparable. It will be high. The performance of the substrate composite as an elastomeric composite is enhanced because the strands shrink and gather into one or more base materials in a relatively uniform finish along the length of the substrate composite.
[0039]
The following example shows that heating the elastic strands reduces the final creep value, ie, increases the creep resistance of the substrate composite incorporating the heated elastic strands. Table 1 shows that a final creep value of, for example, 22.9% is determined using melt blow coating technology at 7 grams per square meter (ie, gm^-2) Is the value obtained for the heat-treated GLOSPAN 840 elastic strand sandwiched between two spunbond webs when the H-2525A adhesive was applied at an application rate of). The GLOSPAN 840 strand was attached to the spunbond web at a stretch of 200%. GLOSPAN 840 is an elastic strand material manufactured by Grove Manufacturing, Fall River, Mass., And comprises a polyester-b-polyurethane block copolymer. Typically, spunbond webs are composed of polypropylene fibers and have a basis weight of 0.5 ounces per square yard. However, the control substrate composite required 10 gm to obtain the same final creep value of 22.9%.^-2H2525A adhesive was required. Thus, heat treatment of the GLOSPAN 840 elastic strand reduced the amount of adhesive needed to achieve a given final creep value.
[0040]
The previous example shows that heating the strands before attaching them to the base material can improve the creep resistance of the substrate composite. As already described, the elastic strands can be heated by hot air or convective heat transfer and conduction, infrared irradiation, or some combination thereof. If the elastic strand or bobbin of elastic strand is heated in another processing step (ie off-line), the strand or bobbin should be heated in a forced air dryer or an electronic oven or under an infrared bulb. Can be. On the other hand, if the strand is heated as part of a process for making the strand or using the strand as a raw material (ie, in-line), the moving strand may be subjected to microwave irradiation, infrared irradiation, The strands can be heated by directing air, or some combination thereof.
[0041]
If the dryer is a device used only to heat the strands, the strands are typically a process used to make the strands or a process that uses the elastic strands as a raw material. It will be heated in another step. To increase the heating rate of the strands, the temperature of the dryer can be raised above 100 degrees, but the temperature cannot be so high because the constituent polymers of the strands deteriorate. However, methods of heating strands based on convection and conduction, such as directing hot air at the strands, can heat the strands in-line in combination with one or more irradiation methods (described below). Please note that.
[0042]
To heat the elastic strands in a separate step (ie, off-line) from the strand manufacturing process or the process using strands as raw material, the strand spools, bobbins, or reels are placed in a dryer at a predetermined temperature, and You can enter only for the time. Alternatively, air heated to a predetermined temperature can be directed to the spool, bobbin, or reel for a predetermined time. Pending application Ser. No. 60 / 171,467, filed Dec. 22, 1999, which is hereby incorporated by reference (and which forms the basis for priority of the present application); As described in the title of the invention, "method for improving strength properties of elastic strand", it can be confirmed whether or not the elastic strand material has deteriorated at a predetermined temperature by using an analysis technique (see Examples described later). ).
[0043]
The spool or bobbin of the strand will either be where the elastic strands are made or where the elastic strands are used as a raw material (if the places where the strands are used are different from the places where the strands are made). Can be placed in a dryer. For example, at the location where the strands were produced, the bobbin of the elastic strands after the initial winding of the strands can be placed in a forced air dryer at a temperature of 102 degrees or higher for 2 hours or more. . Alternatively, it may be placed in a higher temperature forced air dryer for a shorter time. After heat treating the strand, the bobbin may be prepared for transport or may be stored for some time before transport.
[0044]
Other techniques can be used to heat the strand. For example, an infrared light source can be placed near the elastic strand to illuminate the strand. One example of an infrared light source is available from TechniLab Instruments, Inc. of Lequanock, NJ. 250 W infrared light bulb available from the company. The polymer component of the strand generates heat when it absorbs infrared radiation, which heats the strand. In addition, one or more infrared light sources can be placed near the strand after extrusion or spinning, but before it is first wound on a bobbin (ie, in-line at the location where the elastic strand is manufactured). If another processing step is performed in which the bobbin is unwound, processed and then re-wound, the strand can be heat-treated with one or more infrared light sources during this further processing step. .
[0045]
Alternatively, the elastic strands can be irradiated with microwave radiation to heat the strands. Suitable microwave generators and cavities are described in Hedrick et al., U.S. Pat. No. 5,536,921, issued Jul. 16, 1996, which is incorporated herein by reference. The apparatus is useful for processing sheet material online, and can also be used to process elastic strands inline. The apparatus comprises a cylindrical, single-mode resonant cavity microwave applicator (Model TM101) available from International Business Machines, Inc. of Armonk, NY. The diameter of the applicator of this model is 4 inches and the output power can be steplessly adjusted up to 6.0 kW at a frequency of 2450 MHz. The elastic strand can be guided into the cavity such that the strand is exposed to a plurality of microwave standing waves within the cavity. As the elastic material passes through the standing wave, the energy of the incident microwave is converted into heat within the strand. An example of the use of a microwave generator to continuously process a web rather than a strand is described in U.S. Patent No. 5,916,203, the portions of which are incorporated herein by reference. One or more elastic strands can be heated using the same technique.
[0046]
One or more of the specific methods described above may be used in combination to heat one or more elastic strands. For example, one or several infrared light sources can be used in combination with a hot air stream directed at the strand to heat the strand. That is, a high temperature air stream can be directed at the strand before or after exposing the strand to microwave radiation within the cavity as described above. Any combination of methods of transferring energy to the elastic strands to heat the strands, thereby increasing the creep resistance (or reducing the final creep value) of the substrate composite incorporating the heated strands is encompassed by the present invention. Is done.
[0047]
As described in co-pending US patent application Ser. No. 60 / 166,348, in some cases, the bobbin of the elastic strand after first being wound unwinds the bobbin, processes the strand, and then again. It can be processed or treated in several ways by winding the strand. This co-pending application also describes adjusting the exposure of the elastic strands to water vapor to reduce the strength of the strands. Thus, elastic strands heat-treated by the strand manufacturer can be further treated, stored, handled or transported in such a way as to regulate the exposure of the heat-treated strands to water vapor.
[0048]
U.S. Patent Application Ser. No. 60 / 166,348, provides several examples by which the exposure of elastic strands to water vapor can be adjusted. These same methods can be used for elastic strands before, after, or both before and after heat treatment. If the elastic strand has already been heat treated, the heat treated strand bobbin, spool, or reel can be stored in a humidity or temperature controlled room or facility. If the bobbins are transported to another location, the bobbins can be loaded into a container containing a vapor-permeable barrier material. If the elastic strands are placed in a container containing barrier material in a low humidity environment, the microscopic environment around the elastic strands inside the container will correspond to this low humidity environment. After closing the container (eg, heat sealing the plastic bag), the next processing step in which the humidity or temperature outside the container is not regulated can be performed. This container is not opened until the elastic strands are used as raw material in the manufacturing process.
[0049]
Prior to closing the container containing the barrier material, a desiccant can be placed near the elastic strands, including the heat-treated elastic strands, as disclosed in co-pending US patent application Ser. No. 60 / 166,348. This desiccant functions to preferentially adsorb or absorb water vapor until the container allows water vapor to penetrate into and around the elastic strands. Thus, the desiccant helps to maintain the humidity inside the container to a degree that minimizes strength degradation.
[0050]
In another embodiment, before closing the container containing the barrier material, a humidity detector or hygrometer is placed, together with the already already heat-treated elastic strands. When the bag or container is opened after it has been transported to the purchaser of the elastic strand, the humidity detector can be checked to determine if the humidity inside the container has exceeded a certain value. If the humidity exceeds a certain value, it can be returned to the supplier without receiving the bag or container. Alternatively, samples from the shipment can be tested immediately. If the strength properties of the strand are deemed to satisfy the conditions, the transported goods can be accepted and used as raw materials.
[0051]
The bobbin of the elastic strand can be heated where the strand is used as a raw material without heating the strand at the strand manufacturing location. If the elastic strand is not transported in a sealed container containing the barrier material, the elastic strand may be heated when received or after storage and before the strand is used as a raw material. it can. If the elastic strands are stored prior to use, the strands can be stored in a temperature or humidity controlled environment as disclosed in co-pending U.S. patent application Ser. No. 60 / 166,348. .
[0052]
If the elastic strand is transported in a container with barrier material, the elastic strand will not be heated until the container is opened. Thus, for example, a container of elastic strands can be stored until the container is opened. After opening the container and removing the elastic strand bobbin, the bobbin can be placed in a dryer at a selected temperature for a selected time. Alternatively, the bobbin can be placed in a microwave oven to obtain the desired increase in creep value. Microwave radiation, infrared radiation to the elastic strands in some places (ie, in-line) between the payout stand and the location where the strands are attached to the base material to produce the substrate composite without heating the strands off-line. And / or hot air. In each case, the data can be used to select the heat treatment conditions required to achieve a given creep resistance improvement (e.g., the examples described below provide for a given creep or creep resistance at a given creep resistance). It shows that the heat treatment conditions for obtaining the change can be confirmed).
[0053]
A more detailed description of reducing the strength degradation of elastic strands
As described above, the method for improving the creep resistance of the base composite material can be used in combination with the method for controlling the strand exposure to water or water vapor to suppress the decrease in the strength of the elastic strand. Before proceeding with a more detailed description of some exemplary ways in which the exposure of a strand to water or water vapor can be adjusted, it is useful to consider some additional definitions. The term specific humidity generally refers to the mass of water vapor retained per unit mass of gas that does not contain water vapor. As used herein, "specific humidity" refers to the mass of water vapor retained per unit mass of gas that does not contain water vapor, and this gas is typically air. The term relative humidity generally refers to the ratio between the vapor pressure and the vapor partial pressure of a liquid at the vaporization temperature. This is usually expressed as a percentage, 100 percent relative humidity means that the gas is saturated with steam, and 0 percent relative humidity means that the gas is free of steam. As used herein, "relative humidity" refers to the ratio of the partial pressure of water vapor to the vapor pressure of water at gas temperature, and this gas is usually air. As used herein, "humidity" refers to a measure of the amount of water vapor in a gas, usually air, and refers to specific humidity and / or relative humidity unless otherwise specified. The term dew point generally refers to the temperature at which a mixture of vapor and gas cools at a constant humidity and becomes saturated. As used herein, the term "dew point" refers to the temperature at which a mixture of water vapor and a gas is cooled at a constant humidity and saturates, which gas is usually air.
[0054]
One of the ways in which the strand exposure to water vapor can be adjusted is to perform one or more processing and / or processing steps after extrusion or spinning in a humidity controlled environment. This is accomplished by performing one or more of the steps in a room, compartment, or other enclosure having a value corresponding to the humidity of the enclosure controlled to not exceed a selected set point. Achieved. This set value corresponds to the desired specific humidity or relative humidity. Control generally involves first sensing or measuring a value corresponding to specific or relative humidity in the enclosure. Devices used to sense or measure humidity are typically located near elastic strands. The sensed or measured value is transmitted to a controller, computer, or other device that compares the sensed or measured value to a set value. If the sensed or measured value is significantly different from the set value, the specific humidity or relative humidity in the enclosure is forced to adjust to the desired sensed or measured value or below. A control operation is performed.
[0055]
Typically, the specific humidity or relative humidity is forced by directing the air / water vapor mixture across the cooling coils such that the temperature of the mixture falls below the dew point of the mixture. As a result of this cooling process, some of the water vapor condenses on the coil and is removed as a liquid, thereby reducing humidity. By directing a sufficient amount of the air / steam mixture across the cooling coil and then directing the dehumidified air to the enclosure, the humidity is forced to the desired level. After the water vapor condenses and is removed by this cooling process, the air can be heated to reduce the dry bulb temperature. As used herein, "dry bulb temperature" refers to the temperature of an air / steam mixture as indicated by a thermometer contained within the mixture. Thus, as used herein, "humidity controlled" refers to an environment in which the specific humidity and / or relative humidity is controlled, and after the air / steam mixture is dehumidified, air is used to reduce the dry bulb temperature. When heated, the dry bulb temperature of the environment is also controlled or regulated.
[0056]
The air / steam mixture can be collected from the interior of the enclosure and dehumidified and then recirculated back to the enclosure, or collected from outside the enclosure and dehumidified and placed in the enclosure or You can do both. If, for example, the housing is formed around a take-up stand on which the elastic strands are continuously guided, the housing includes an opening through which the strands can enter and be wound. If the manufacturing environment is hot and humid, it is preferable to maintain a slight positive pressure inside the housing in order to reduce the amount of hot and humid air entering through the opening. In this case, some amount of the air / steam mixture outside the housing is dehumidified to recover the air / steam mixture inside the housing that exits through the opening due to positive pressure. It is necessary to put in.
[0057]
Rather than controlling the humidity to be at or below a set point, the air in a room or enclosure may be cooled to a set temperature such that the maximum specific humidity does not exceed a certain level. Using an air humidity chart at atmospheric pressure, an appropriate set temperature can be selected. For example, when the relative humidity is just 100% at a temperature of 40 degrees Fahrenheit, the specific humidity is Ib of dry air._mThe amount of water vapor per unit is about 0.006Ib_mBecomes This value is less than 1/4 of the specific humidity resulting from a 60% reduction in peak load value after 60 days (see Examples below). Thus, "temperature controlled" as used herein refers to an environment in which the temperature is controlled to a certain value to regulate the amount of water vapor exposed to the elastic strand.
[0058]
As mentioned above, one embodiment of the present invention is directed to controlling the humidity of one or more processing and / or processing steps after extrusion or spinning. Alternatively, the temperature of one or more processing and / or processing steps can be controlled so that the water vapor retention of the air is limited. For example, the step of first winding the elastic strands on the winder can be performed in a humidity or temperature controlled environment. Processing steps upstream or downstream of the first winder can also be performed in a humidity controlled or temperature controlled environment. As used herein, "first winder" refers to a winder on which a strand is first wound after being extruded or spun, and "upstream" refers to a first winder after the strand is extruded or spun. The term "downstream" refers to a processing step performed before the first winding machine, and the term "downstream" refers to a processing step performed after the first winding machine. One or more additional processing steps are performed after the first winding step on another unwind / winding table (ie, a table where the elastic strands are unwound, processed in some way, and re-wound). In some cases, one or more of these additional processing steps may be performed in a humidity and temperature controlled environment. If the bobbin of elastic strands is stored before use or transport, it can be stored in a humidity controlled or temperature controlled environment. If the elastic strands are transported to another location, the elastic strands are unwound and then re-wound and the steps of preparing the elastic strands, including the further steps of being packaged for transport, are controlled by humidity or temperature. It can also be performed in a different environment. Also, the step of transporting or transporting the elastic strands can itself be performed in a humidity controlled or temperature controlled environment.
[0059]
All of these steps of winding, storing, preparing and packaging for transport (if transport is required), transporting, and re-storage where the strands will be used as raw materials are all performed on the production machine. The tensile strength of the strands when used as is about 20%, especially about 10%, and more specifically about 10%, from the tensile strength of the strands when initially manufactured or prepared for transport. It can be done in a humidity controlled or temperature controlled environment so that it does not decrease by more than 5%.
[0060]
However, in some cases, not all steps need to be performed in a humidity or temperature controlled environment. For example, elastic strands can be placed in a container having barrier material. As used herein, "barrier material" refers to a material that is resistant to the ingress of water vapor. The step of placing the elastic strands in a container with barrier material, ie, packaging the elastic strands for storage or transport, can be performed in a number of ways. The elastic strand bobbin or pellets of the elastic strand bobbin can be packaged or wrapped with a barrier material, for example, by suitable shrink wrap. Alternatively, the elastic strand bobbin or pellets of the elastic strand bobbin can be packaged in a soft plastic bag of barrier material. That is, it can be placed in a box or carton containing a barrier material, for example, lined or held with a soft plastic bag that is resistant to the ingress of water vapor. Other types of containers including barrier materials can also be used. When the elastic strand is put in a container containing a barrier material while having a low humidity environment, the microscopic environment near the elastic strand inside the container corresponds to the low humidity environment. The following processing steps can be performed such that the humidity or temperature outside the container is not adjusted. The container is not opened until the elastic strand is used as a raw material in the manufacturing process.
[0061]
Many methods can be used to package the elastic strand. The elastic strands can be wound or unwound on a first winder in a humidity-controlled or temperature-controlled environment and guided or transported to a humidity-controlled or temperature-controlled environment for packaging. Alternatively, the elastic strands can be wound on a first winder and then immediately removed and directed or transported to a humidity or temperature controlled environment for packaging.
[0062]
In a humidity controlled or temperature controlled environment, the elastic strand bobbins or the elastic strand bobbin pellets are placed in a container containing the barrier material. Suitable barrier materials having resistance to the ingress of water vapor include, but are not limited to, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyester, polycarbonate, nylon, cellulose, or some combination thereof. including. The container is then closed in such a way as to minimize the amount of water vapor that can reach the packaged strand during the next storage and / or transport step. For example, if the container containing the barrier material is a soft polyethylene bag or other soft water-resistant plastic bag, heat seal after placing the elastic strand bobbin or pellets of the elastic strand bobbin in this bag. Can be. Alternatively, the elastic strand bobbin or pellets of the elastic strand bobbin may be placed in a carton or box lined with a barrier material, such as a polyethylene bag, and the bag is heat sealed after the elastic strand is placed.
[0063]
A desiccant may be placed near the elastic strands before closing the container containing the barrier material, for example, before heat sealing. This desiccant functions to preferentially adsorb or absorb water vapor until the container allows water vapor to penetrate into and around the elastic strands. Thus, the desiccant helps to maintain the humidity inside the container to a degree that minimizes strength loss.
Examples of useful desiccants include calcium chloride, calcium sulfate, silica gel, molecular sieves, Al₂O₃Or some combination of these. The desiccant is typically placed in a container that allows water vapor to enter and contact the desiccant and keep the desiccant away from the elastic strands. Examples of containers are fibrous webs of natural fibers, usually containing cellulose as the main component, or pouches made of non-woven materials, such as polyethylene or polypropylene non-woven fabrics formed to be permeable to water vapor.
[0064]
In another aspect, the invention further comprises the step of replacing the air / water vapor mixture with a dry inert gas inside the container containing the barrier material before closing the container. For example, after placing the elastic strand bobbin pellets inside the container, a soft conduit can be used to guide dry nitrogen gas into the container. After sufficient time has passed for the air / steam mixture to be pushed out of the interior of the container, the conduit is removed from the container and the container is then closed. This replacement step can also be performed in combination with the step of placing the desiccant with the elastic strands before closing the container. In another method, the packaging system can be configured such that the air / water vapor mixture inside the container containing the barrier material is withdrawn before the container is closed.
[0065]
In another aspect, before closing the container containing the barrier material, a humidity detector is placed with the elastic strands. When the bag or container is opened after being transported to the purchaser of the elastic strand, the humidity detector can be checked to determine if the humidity inside the container has exceeded a certain value. If the humidity exceeds a certain value, it can be returned to the supplier without receiving the bag or container. Alternatively, samples from the shipment can be tested immediately. If the strength properties of the strand are deemed to satisfy the conditions, the transported goods can be accepted and used as raw materials. One example of a suitable humidity detector is a hygrometer corresponding to catalog number HC-10 / 60-200 available from Omega Engineering, Inc. of Stanford, Connecticut. The hygrometer is capable of detecting relative humidity ranging from 10 percent to 60 percent.
Placing the humidity detector with the elastic strands, placing a desiccant with the strands before the container containing the barrier material is closed, drying the air / water vapor mixture inside the container containing the barrier material before the container is closed It can be performed in combination with the step of replacing with the inert gas described above, or both steps.
[0066]
In some embodiments of the present invention, the bobbins of the elastic strands are stored at the location where the strands are made and / or where the strands are used as a raw material. During this storage step, the strand is unpackaged and it is stored for more than 10 days, in particular for more than 20 days, more particularly for more than 30 days, and its ambient humidity is The room, facility or area in which the strands are stored can be in a humidity controlled or temperature controlled environment if the strength of the strands is significantly reduced. However, as described above, regardless of the entire time between extruding or spinning the strand and using the strand as a feedstock, the strand was extruded or spun to minimize or eliminate loss of strength. Later, all of the processing and processing steps can be performed in a humidity controlled or temperature controlled environment. That is, the elastic strands are packaged such that the "microenvironment" inside the container containing the barrier material has a low water vapor content (ie, low humidity), thereby eliminating the need to control the external environment of the package, Later processing steps can be performed.
[0067]
Elastic strands processed or treated according to the present invention can be incorporated into many substrate composites and disposable absorbent articles. Examples of such substrate composites and / or disposable absorbent articles are described in U.S. Pat. No. 4,940,464, entitled "Disposable Incontinence Clothing or Training Pants," the portions of which are incorporated herein by reference. No., description of the use of elastic strands in the storage flaps from line 7 to line 34 in paragraph 7, and description of the elastic members in line 9 to line 36 in paragraph 9 from paragraph 9 U.S. Pat. No. 5,904,675, entitled "Absorptive Article with Improved Elastic Edge and Storage System," and an elastic leg member from line 39 of paragraph 11 to line 2 of paragraph 12 No. 5,904,67, entitled "Absorptive Article with Improved Waist Area Drying and Method of Making Same", which is incorporated herein by reference. US Pat. No. 6,078,098 entitled "Absorptive article having water collecting grooves", which is hereby incorporated by reference and the description of the stretchable legs and waist members from line 18 to line 48 in paragraph 4 is incorporated herein by reference. No. 5,902,297. The present invention is applicable to other structures, composites, or products that incorporate one or more elastic strands that have been heat treated to improve creep resistance (or reduce final creep), and have a high strength. It is to be understood that the exposure to water and / or water vapor is adjusted to reduce the degradation.
[0068]
Examples of methods and apparatus for making laminate webs of elastomers (ie, substrate composites incorporating elastic strands for the purposes of the present invention) that can be used with the present invention are described in US Pat. No. 5,964,973. The invention is found in the title "Method and Apparatus for Making an Elastomeric Laminate Web" and as mentioned above, the parts relevant to the invention are hereby incorporated by reference. This patent provides an example of a method and apparatus for incorporating elastic strands into a substrate composite, which is heat treated to improve the uniformity of adhesion between the elastic strands and the base material and its strength. It should also be understood that the elastic strands of the present invention can also be used in other methods and devices to form a substrate composite.
[0069]
(Example)
Example 1
GLOSPAN 840 (Globe) bobbin, an elastic strand consisting of a polyester-b-polyurethane block copolymer, was obtained from Globe Manufacturing. The GLOSPAN 840 bobbin had a 3 inch radius, 10 inch long plastic core. The GLOSPAN 840 elastic strand was wrapped around each plastic core such that the outer surface formed by the strands extended radially outward from the outer surface of the plastic core approximately 3 inches. In this particular experiment, the strand was manufactured within two weeks of our obtaining a bobbin from Globe Manufacturing. In addition, the elastic strands were coated with a silicone-based lubricant. The bobbin was placed in a plastic bag and sealed. The bag containing the bobbin was placed in a Blue M Corp., Blum Island, Ill., Model OV-490A-2 forced air dryer. The dryer was preheated to a temperature of 102 ° C. before placing the plastic bags. After 4 hours of exposure to the selected temperature, the bag containing the GLOSPAN 840 bobbin was removed from the dryer.
[0070]
Approximately 24 hours had passed before the bobbin was removed from the dryer and mounted on the payout stand to make the various substrate composites. The substrate composite was made on equipment available from J & M Laboratories, Dawsonville, Georgia. Each of the bobbins was placed on a payout stand. As shown in FIG. 4, individual strands from the bobbin were led to a nip 106 between two rolls of a 4 inch diameter rubber roll 110 and a 6 inch diameter steel roll 104. A base material 102, in this case a non-woven web, was guided from a corresponding payout stand (not shown) to the surface of the steel roll and further through the nip. A second nonwoven web 108 was guided from its payout stand (not shown) to the surface of the rubber roll and further through the nip. The device was typically operated at a rate of 100 feet per minute.
[0071]
The elastomeric strand 100, in this case GLOSPAN 840, was guided further through the comb 112 from a corresponding payout stand (not shown) so that the elastic strand was sandwiched between the two nonwoven webs. The comb provides the desired lateral distribution of the strands and serves to maintain it. The strands were placed approximately 5 mm apart from each other over the width of the base material, in this case a nonwoven web.
[0072]
The speed of the strand unwind stand relative to the rotation speed of the steel and rubber rolls was such that the strands were stretched to about 200% of that when applied to a nonwoven web by application of an adhesive. The adhesive applied was in this case an H-2525A hot melt adhesive available under the alphanumeric designation of Atfindlay, Inc. of Wauwatosa, Wisconsin. The adhesive is 4 grams per square meter (ie, gm^-2), 7gm^-2, And 10gm^-2At three different coating weights. For each of these three coats, the adhesive was applied using one of two air deposition techniques, swirl coat or melt blow coat.
[0073]
The applicator 114 used to apply the adhesive, regardless of the amount of coating or the use of air deposition techniques, has the nozzle front shown substantially parallel to the surface of the web to which the adhesive is first applied, and the surface of the web 1.5 inches 116 from the position. Further, the central axis of the nozzle shown, perpendicular to the web to which the adhesive was first applied, was 8 inches 118 from a parallel axis through the nip formed by the rubber and steel rolls.
[0074]
Table 1 shows the following variables for a number of substrate composites: (1) the air deposition technique used to apply the H-2525A adhesive (swirl or meltblown), (2) H- Application amount of 2525A adhesive (4 gm^-2, 7gm^-2Or 10gm^-2(3) (2 spunbond webs having a basis weight of 0.5 ounces per square yard, made of polypropylene fibers and serving as two base materials, or spunbond-meltblown-spunbond materials) Two base materials of a three-layer laminate, wherein the entire laminate has a basis weight of about 0.6 ounces per square yard and each of the three layers is a spunbond or meltblown laminate of polypropylene fibers A) the type of base material with the elastic strands interposed between them; and (4) whether the elastic strands were heated using the procedure described above prior to attaching the strands to the base material to form a substrate composite. FIG. 3 shows the results of a number of experiments measuring final creep as a function of.
[0075]
The results (see Table 1) show that the heated GLOSPAN 840 according to the present invention reduces final creep, ie, increases creep resistance. In addition, heating of the elastomer can reduce the amount of adhesive required to achieve a given final creep value. For example, 7 gm of H-2525A adhesive is applied using a melt blow coating technique.^-2A final creep value of 22.9% was obtained for a GLOSPAN 840 elastic strand that was heat treated and sandwiched between two spunbond webs. However, the control substrate composite incorporating GLOSPAN 840, which had not been heat treated, had a 10 gm 10 gm to achieve the same final creep value of 22.9%.^-2Of H-2525A adhesive applied.
[0076]
Table 1

[0077]
Example 2
LYCRA 940 bobbin, an elastic strand of polyether-b-polyurethane block copolymer, was obtained from DuPont, Wilmington, Del. The LYCRA 940 bobbin had a plastic core with a radius of 3 inches and a length of 4 inches. The LYCRA 940 elastic strands were wrapped around each plastic core such that the outer surface formed by the strands extended radially outward from the outer surface of the plastic core approximately 3 inches. In this particular experiment, the strand was manufactured within two weeks of our obtaining bobbins from DuPont. Each bobbin was placed in a forced air dryer, Model OV-490A-2, manufactured by Blue M, Inc., Blum Island, Illinois. The dryer was preheated to a temperature of 102 ° C. before the bobbins were placed in the dryer. After 4 hours of exposure to the selected temperature, the LYCRA 940 bobbin was removed from the dryer.
[0078]
Approximately 24 hours had passed before the bobbin was removed from the dryer and mounted on the payout stand to produce various substrate composites. The substrate composite was made on equipment available from J & M Laboratories, Dawsonville, Georgia. Each of the bobbins was placed on a payout stand. As shown in FIG. 4 (see the previous example, where the drawing numbers correspond to the parts of the apparatus identified), the individual strands from the bobbin are separated by a 4 inch diameter rubber roll and a 6 inch diameter steel roll. Led to the nip between the two rolls. The base material, in this case a non-woven web, was guided from the corresponding payout stand (not shown) to the surface of the steel roll and further through the nip. A second nonwoven web was guided from its payout stand (not shown) to the surface of the rubber roll and further through the nip. The device was typically operated at a rate of 100 feet per minute.
[0079]
An elastomeric strand, in this case LYCRA 940, was guided through a comb from a corresponding payout stand (not shown) to the nip such that the elastic strand was sandwiched between the two nonwoven webs. The comb serves to provide and maintain the desired lateral distribution of the strands. The strands were placed approximately 5 mm apart from each other over the width of the base material, in this case a nonwoven web.
[0080]
The speed of the strand unwind stand relative to the rotation speed of the steel and rubber rolls was such that the strands were stretched to about 200% of that when applied to a nonwoven web by application of an adhesive. The adhesive applied was in this case an H-2525A hot melt adhesive available under the alphanumeric designation of Atfindlay, Inc. of Wauwatosa, Wisconsin. The adhesive is 4 grams per square meter (ie, gm^-2), 7gm^-2, And 10gm^-2At three different coating weights. For each of these three coats, the adhesive was applied using one of two air deposition techniques, swirl coat or melt blow coat.
[0081]
The applicator used to apply the adhesive, regardless of the amount of coating or the use of air deposition techniques, has the illustrated nozzle front approximately parallel to the surface of the web to which the adhesive is first applied, from the surface of the web. It was arranged to be at a 1.5 inch position. Further, the central axis of the nozzle shown, perpendicular to the web to which the adhesive was first applied, was 8 inches from the parallel axis through the nip formed by the rubber and steel rolls.
[0082]
Table 2 shows the following variables for a number of substrate composites: (1) the air deposition technique used to apply the H-2525A adhesive (swirl or meltblown), (2) H- Application amount of 2525A adhesive (4 gm^-2, 7gm^-2Or 10gm^-2(3) (2 spunbond webs having a basis weight of 0.5 ounces per square yard, made of polypropylene fibers and serving as two base materials, or spunbond-meltblown-spunbond materials) Two base materials of a three-layer laminate, wherein the entire laminate has a basis weight of about 0.6 ounces per square yard and each of the three layers is a spunbond or meltblown laminate of polypropylene fibers A) the type of base material with the elastic strands interposed between them; and (4) whether the elastic strands were heated using the procedure described above prior to attaching the strands to the base material to form a substrate composite. FIG. 3 shows the results of a number of experiments measuring final creep as a function of.
[0083]
This result indicates that the heated LYCRA 940 according to the present invention reduces final creep, ie, increases creep resistance. In addition, heating of the elastomer can reduce the amount of adhesive required to achieve a given final creep value. For example, 4 gm of H-2525A adhesive is applied using a swirl coating technique.^-2A final creep value of 46.3% was obtained for the LYCRA 940 elastic strands that were heat treated and sandwiched between the two spunbond webs. However, the control substrate composite incorporating LYCRA 940, which had not been heat treated, required 7 gm to achieve the same final creep value of 46.3%.^-2Of H-2525A adhesive applied.
[0084]
Table 2

[0085]
Example 3
Thermogravimetric analysis and differential scanning calorimetry were used to determine the thermal stability of GLOSPAN 840 samples. In the thermogravimetric analysis, a sample of GLOSPAN 840 was placed in a sample holder in the heating element of a thermogravimetric analyzer model 951, manufactured by TA Instruments, Newcastle, Delaware. The sample was heated from a room temperature of about 21 ° C to a temperature of 450 ° C at a heating rate of 10 ° C per minute. The sample was heated under a dynamic atmosphere of air with an air flow of approximately 80 millimeters per minute. The crucible was weighed continuously during heating so that any weight loss could be detected. The resulting weight change curve or plot of sample weight versus temperature showed that the decomposition temperature of GLOSPAN 840 was about 240 ° C. in air.
[0086]
For analysis using differential scanning calorimetry, a 10 milligram sample of GLOSPAN 840 was placed in the sample chamber of the heating / cooling block of a TA Instruments differential scanning calorimeter model 2920. The sample was heated from -100C to 200C at a heating and cooling rate of 10C per minute, then cooled to -100C and reheated to 200C. An accessory for cooling liquid nitrogen, also made by TA Instruments, was attached to the differential scanning calorimeter model 2920. The results showed that in the temperature range from about 20 ° C. to about 200 ° C., there was no large peak indicating energy absorption or release. Therefore, GLOSPAN 840 appears to be stable to oxidation and heat in this temperature range.
[0087]
Example 4
GLOSPAN 840 (Globe) bobbin, an elastic strand consisting of a polyester-b-polyurethane block copolymer, was obtained from Globe Manufacturing. This elastic strand was coated with a silicone-based lubricant. A sample of this strand was placed in a controlled environment where the temperature was controlled to a value of 100 degrees Fahrenheit and the relative humidity was controlled to a value of 80%. At selected times of exposure to these conditions, a sample of the strand was removed from the controlled environment and transferred to the test room. Approximately 15 to 30 minutes were spent removing the sample from the controlled environment and testing the sample.
[0088]
Both the tensile strength and elongation of the strand samples were measured using a Syntec tensile tester available from MTS System Corporation, Eden Prairie, Minnesota. The opposing holder of the tensile tester consisted of a cylindrical rod. The gauge length was set to 1.5 inches by moving the holder so that the distance between the rod center axes was 1.5 inches. One end of the length of the strand was then wrapped twice around one cylindrical rod. The other end was then removed and wrapped twice around the other cylindrical rod. The tester was then operated such that the opposing holder moved in the opposite direction at a crosshead speed of 20 ± 0.4 inches per minute. The strand was stretched at this speed until it broke. At the location where the strand broke, the peak load value (grams) and elongation (percent) were recorded, reflecting the change in length per unit length. In this test process, exposure under specified conditions of relative humidity and temperature was repeated a selected number of times, resulting in the following tensile strength (ie, peak load value) (each value was between 5 and 10): It reflects the average of up to repetitions). The peak load value of the strand before exposure to 100 degrees Fahrenheit and 80% relative humidity is about 375 grams (elongation is about 1080%) and the peak after about 5 days of exposure to this particular condition The load value decreases to about 345 grams (extension is about 1175%) and the peak load value after approximately 18 days of exposure to this particular condition decreases to about 250 grams (extension is about 1200). %), The peak load value after exposure to this particular condition for approximately 30 days is reduced to about 245 grams (elongation about 1145%), and after approximately 65 days of exposure to this particular condition. Decreased to about 150 grams (elongation about 870%). This data indicates that water vapor reduces the strength of the elastic strand.
[0089]
Example 5
A sample identical to the GLOSPAN 840 bobbin described in Example 1 was placed in a controlled environment at a temperature of 120 ° F. and a relative humidity of 20%. Using the same procedure as described in Example 1, a sample of this strand was tested for exposure to this condition a selected number of times, with the following results (each value ranging from 5 to 10 It reflects the average of up to repetitions). The peak load value of the strand before exposure to 120 degrees Fahrenheit and 20% relative humidity is about 375 grams (elongation is about 1080%) and the peak after about 50 hours of exposure to this particular condition The load value is about 400 grams (extension is about 1125%) and the peak load value after approximately 180 hours of exposure to this particular condition is about 455 grams (extension is about 1250%); The peak load value after exposure to this particular condition for approximately 500 hours was about 410 grams (elongation was about 1275%). This data shows that adjusting the exposure of the elastic strands to water vapor reduces the amount of strength loss due to the action of water on the strands.
[0090]
Although the present invention has been described in considerable detail with respect to particular embodiments, other variations are possible. The spirit and scope of the appended claims is not to be limited to the specific forms described herein.
[Brief description of the drawings]
FIG.
FIG. 2 is a cross-sectional view of one of the devices for making elastic strands.
FIG. 2
FIG. 2 is a cross-sectional view of one of the devices for making elastic strands.
FIG. 3
It is a figure which shows the state of the base | substrate composite material when the change by a creep test is given sequentially.
FIG. 4
FIG. 4 is one side view of a process for attaching one or more elastic strands to at least one base material.

Claims (30)

A method for improving the creep resistance of a substrate composite comprising at least one elastic strand, comprising:
Prepare elastic strands,
Heating the strand,
Disposing the strand to be located between the first base material and the second base material;
The strands, the first base material, the second base material, or these so that at least a portion of the strand adheres to at least a portion of the first base material and at least a portion of the second base material. Applying an adhesive to some combination of the
Heating the strands to increase the creep resistance of the substrate composite by about 5% or more compared to a substrate composite made under substantially the same conditions except that the elastic strands are not heated. A method characterized by increasing. The method of claim 1, wherein the creep resistance of the substrate composite is increased by about 10% or more. The method of claim 1, wherein the creep resistance of the substrate composite is increased by about 15% or more. The first base material and the second base material are a single, identical material, and the strands are disposed between folded portions of the material and attached to one or both of its inner surfaces The method of claim 1, wherein: The elastic strand is made of polyester, polyurethane, polyether, polyamide, polyacrylate, polyester-b-polyurethane block copolymer, polyether-b-polyurethane block copolymer, or polyether-b-polyamide block copolymer. The method of claim 1, wherein the method comprises: The method according to claim 5, wherein the strand is coated with a lubricant. The method of claim 5, wherein the strand is heated by directing hot air, infrared, or microwave radiation at the strand. The method of claim 5, wherein the strand is heated by placing the bobbin of the strand in a heated environment at an air temperature between 100C and 200C for 2 hours or more. The method of claim 5, wherein the strand is heated by placing the bobbin of the strand in a heated environment at an air temperature between 100C and 200C for 4 hours or more. A method for improving the creep resistance of a substrate composite comprising at least one elastic strand, comprising:
Providing an elastic strand consisting of a polyester-b-polyurethane block copolymer or a polyether-b-polyurethane block copolymer and prepared by steps including lubricating its surface;
Heating said strands before attaching to the base material,
Attaching the strands to the base material at a coverage of 4 grams per square meter or more using an adhesive;
Wherein the heating step comprises exposing the strand to hot air, infrared, microwave radiation, or a combination thereof, wherein the creep resistance of the substrate composite comprising the heat treated elastic strand is heat treated. A creep resistance value of at least about 5% greater than a creep resistance value of the substrate composite including no elastic strands. During manufacture of the strand, during storage of the strand at the geographical location where the elastic strand was manufactured, the geographical location where the elastic strand was manufactured and the geographical location where the elastic strand will be used as a raw material During storage of the strand in a geographical location where the elastic strand is to be used as a raw material, during use of the elastic strand as a raw material, or some combination thereof. Adjusting the exposure of the elastic strands to water vapor before, during or after heating such that the specific humidity around the strand does not exceed about 0.01 pounds of water vapor per pound of dry air. The method of claim 2, further comprising: The method according to claim 11, wherein the elastic strand is used as a raw material for producing a base composite material including the elastic strand or an absorbent article including the elastic strand. 13. The method of claim 12, wherein the specific humidity around the elastic strand does not exceed about 0.005 pounds of steam per pound of dry air. During transport of the elastic strand from the geographical location where the elastic strand was manufactured to the geographical location where the elastic strand is to be used as a raw material, the exposure of the elastic strand to water vapor is adjusted. 13. The method of claim 12, wherein the method comprises: The method of claim 14, wherein adjusting the exposure of the strand to water vapor comprises controlling a temperature around the strand or around a container containing the strand. The method of claim 15, wherein the temperature is controlled to a value not exceeding about 55 degrees Fahrenheit. The method of claim 14, wherein adjusting the exposure of the strands to water vapor comprises controlling humidity around the strands or around a container containing the strands. 3. The method of claim 2, further comprising controlling the exposure of the elastic strands to the water vapor before, during, or after heating, placing the strands in a container containing a barrier material.
Closing said container,
A method comprising an additional step. When the container containing barrier material is at a time after the strand was first manufactured and when transporting the strand from the geographical location at which the strand was originally manufactured to the geographical location using the strand. the method according to claim 18, characterized in that it is closed at a time t ₁ which is an earlier time. Specific humidity around the strands, the time t _1, the water vapor mass per pound of dry air between the time the time t ₂ is when the closed container with a barrier material is initially opened 0.017 20. The method of claim 19, wherein the weight does not exceed pounds. The specific humidity around the strand is such that between time t ₁ and time t ₂ , the time when the closed container with the barrier material is first opened, there is 0.01% water vapor per pound of dry air mass. 20. The method according to claim 19, wherein the weight does not exceed one pound. When the specific humidity around the strand is between time t ₁ and time t ₂ , the time when the closed container with the barrier material is first opened, there is 0,0 steam per pound of dry air mass. 20. The method according to claim 19, wherein the method does not exceed 005 mass pounds. 21. The method of claim 20, wherein the barrier material comprises polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyester, polycarbonate, nylon, cellulose, or a combination thereof. 24. The method of claim 23, wherein closing the container containing barrier material comprises heat sealing the container, the barrier material, or both. 25. The method of claim 24, further comprising placing a desiccant with the strands before heat sealing the container, the barrier material, or both. The drying agent is calcium chloride, calcium sulfate, silica gel, molecular sieve, the method according to claim 25, characterized in that of Al 2 _{O 3,} or combinations some of these. Prior to heat sealing the container, the barrier material, or both, replacing any mixture of air and steam inside the container containing the barrier material with an inert dry gas, the container, the barrier material, or 27. The method of claim 24, 25, or 26, further comprising placing a hygrometer inside the container containing the barrier material, or both, before heat sealing both. An elastic strand which is treated or processed by the method according to claim 1, 5, 6, 9, 16, 17, 18, 22, or 23. A substrate composite comprising the elastic strand of claim 28. A disposable absorbent product comprising the substrate composite of claim 29.