JP3664189B2 - Adhesive sheet - Google Patents

Description

【００１４】
本発明は、この膨潤率が５０％以上である粘着剤を用いることが必要である。因みに、粘着剤層の水に対する膨潤率が５０％未満の場合には、離解工程における粘着剤層の膨潤が不十分であるために、パルプより粘着剤成分を十分に分離することが不可能であり、結果的に再生パルプにおける粘着剤成分の残存率が高くなってしまう。
【００１５】
このような膨潤率を満足する粘着剤を用いても、粘着剤層中の水可溶成分の含有率が３〜４０％であると更にこの範囲である粘着剤層は、粘着剤層を水に浸漬した際に、粘着剤層への水の浸透が良好で且つ粘着剤層が部分的に水に溶解するので粘着剤層皮膜は脆くなり、離解工程での大きな撹拌力によって容易に微粒子状に変化させることができ、離解工程の後工程である粗選、精選及びフローテーション等の各工程で粘着剤成分を除去することが可能となるので好ましい。因みに、粘着剤層における水可溶成分が３％未満の場合は、粘着剤層への水の浸透性が劣り、逆に４０％を越える場合は、粘着物性の面で粘着剤の凝集力が乏しくなり実用的でなくなる。
【００１６】
更に、古紙の離解工程において粘着剤層皮膜を容易に微粒子状に変化させるには、粘着剤層の水浸漬後における破断強度が２kgf/cm² 以下であることがより好ましい。因みに、粘剤層の水浸漬後における破断強度が２kgf/cm² を越える場合は、離解工程において粘着剤層皮膜を微粒子にすることができず、離解工程の後工程である粗選、精選及びフローテーション等の各工程で粘着剤成分を除去することが不十分となり、結果的に再生パルプにおける粘着剤成分の残存率が高くなってしまう。
【００１７】
なお、粘着剤の水浸漬後の破断強度は、次のようにして求めた値である。
先ず、ポリエチレンラミネート紙を基材にした剥離の重さの異なる二種類の剥離シートを用意する。この剥離シートの一方に、塗布量が乾燥重量で１００ｇ／ｍ² となるように粘着剤層を形成し、他方の剥離シートを積層する。即ち、剥離シートＡ／粘着剤層／剥離シートＢの構成にする。
次に、得られた粘着シートを巾２０ｍｍ、長さ１２０ｍｍの形に切断し、さらに剥離シートＡ及び剥離シートＢを剥がし粘着剤層の試験片を作る。得られた試験片を水に浸漬して１時間後に、ＪＩＳ−Ｋ−６３０１の引張り強さの測定方法に準拠して粘着剤層皮膜の切断に至る最大荷重を測定し、下記計算式により破断強度を求める。（単位：kgf/cm² ）
【００１８】
【数２】

【００１９】
上記の条件を満足する粘着剤層を形成する粘着剤としては、例えば、下記のモノマー組成のような、（ポリ）エチレングリコール（メタ）アクリレートモノマーを必須成分として含有する（メタ）アクリル酸エステル共重合体を使用した粘着シートが、本発明の再離解性に優れた粘着シートのひとつの好ましい形態としれ挙げられる。
【００２０】

【００２１】
かかる（ａ）（ポリ）エチレングリコール（メタ）アクリレートモノマーとしては、〔化１〕の如き一般式に表される化合物である。
【００２２】
【化１】

【００２３】
（ここに、Ｒ₁ はメチル基または水素原子、またＲ₂ はメチル基またはフェニル基をそれぞれ示す。なお、ｍは１〜１０の整数である。）
【００２４】
なお、これら（ａ）（ポリ）エチレングリコール（メタ）アクリレートモノマーは、５〜４０重量％の範囲で共重合させる必要がある。因みに、５重量％未満では、水再離解性が不十分となる。一方これら親水性モノマーの配合率が増せば粘着剤皮膜の親水性が増して離解性が向上するが４０重量％を越えると、粘着剤の凝集力が低下して、粘着シートの機能が低下する。
【００２５】
また、（ｂ）（メタ）アクリル酸のＣ₄ 〜Ｃ₁₈アルキルエステルモノマーとしては、例えば（メタ）アクリル酸ブチル、（メタ）アクリル酸ヘキシル、（メタ）アクリル酸オクチル、（メタ）アクリル酸−２−エチルヘキシル、（メタ）アクリル酸ステアリル等が挙げられる。そして、これらモノマーの共重合体部分に占める割合は、２０〜８０重量％の範囲で共重合される。因みに、２０重量％未満では、粘着剤の粘着力が乏しく、また、８０重量％を越えると、水再離解性が不十分となる。
【００２６】
また、（ｃ）エチレン性不飽和カルボン酸含有モノマーとしては、例えば、アクリル酸、メタクリル酸、クロトン酸、マレイン酸、フマル酸、モノアルキルマレイン酸、モノアルキルイタコン酸、モノアルキルフマル酸等が挙げられる。そして、これらモノマーの共重合体部分に占める割合は、０〜２０重量％の範囲で共重合される。因みに、２０重量％を越えると、粘着剤の粘着力が不十分となる。
【００２７】
さらに、上記の（ａ）（ポリ）エチレングリコール（メタ）アクリレートモノマー、（ｂ）（メタ）アクリル酸のＣ₄ 〜Ｃ₁₈アルキルエステルモノマー、および（ｃ）エチレン性不飽和カルボン酸含有モノマー と共重合可能な他のモノマーとしては、例えば、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸シクロヘキシル、（メタ）アクリル酸メトキシエチル、（メタ）アクリル酸エトキシエチル、（メタ）アクリル酸ジメチルアミノエチル、（メタ）アクリル酸ジエチルアミノエチル、（メタ）アクリル酸グリシジル、酢酸ビニル、プロピオン酸ビニル、塩化ビニル、塩化ビニリデン、スチレン、ジビニルベンゼン、エチレン、（メタ）アクリロニトリル、（メタ）アクリルアミド、Ｎ−ブトキシメチル（メタ）アクリルアミド、Ｎ，Ｎ’−メチレンビス（メタ）アクリルアミド、及び例えば下記の一般式〔化２〕で表されるカルボン酸変成ロジンエステルモノマー等が挙げられる。
【００２８】
【化２】

【００２９】
（式中、Ｒ₃ は水素原子またはメチル基を示し、ｎは１〜８の整数を表す。）
【００３０】
そして、共重合体に占めるこれらモノマーの割合は、１〜４０重量％の範囲で調節される。因みに、１重量％未満では粘着剤が軟らかくなりすぎ、逆に４０重量％を越えると粘着剤が硬くなりすぎて粘着シートの機能が低下するため好ましくない。
【００３１】
なお、これらの共重合可能な他のモノマーの中でも、特に（メタ）アクリル酸メチル、（メタ）アクリル酸ジメチルアミノエチル、（メタ）アクリル酸グリシジル、ジビニルベンゼン、（メタ）アクリロニトリル、（メタ）アクリルアミド、Ｎ−メトキシメチル（メタ）アクリルアミド、Ｎ−ブトキシメチル（メタ）アクリルアミド、Ｎ，Ｎ’−メチレンビス（メタ）アクリルアミド、〔化２〕で表されるカルボン酸変成ロジンエステルモノマー等がガラス転移温度、接着性能等の面から好ましい。
【００３２】
なお、上記の共重合体の製造方法については、特に限定されるものではなく、例えば、水、溶剤、連鎖移動剤、重合開始剤等の存在下で溶液重合する方法や、乳化剤、連鎖移動剤、重合開始剤、分散剤等の存在下の水系でエマルション重合する方法にて製造される。
【００３３】
なお、重合時のモノマーの濃度は、通常３０〜７０重量％、好ましくは４０〜６０重量％程度が適当である。また、重合の際に使用される重合開始剤としては、例えば過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩、２，２’−アゾビスイソブチロニトリル、２，２’−アゾビス（２，４−ジメチルバレロニトリル）等のアゾ系化合物、過酸化水素、ベンゾイルパーオキサイド、ラウリルパーオキサイド等の過酸化物、過硫酸アンモニウムと亜硫酸ソーダ、酸性亜硫酸ソーダ等との組み合わせからなる、所謂レドックス系の重合開始剤等が挙げられる。
上記重合開始剤の使用量は、通常重合に供するモノマー全量に対して、０．２〜２重量％、より好ましくは、０．３〜１重量％の範囲で調節される。
【００３４】
さらに、共重合に際して添加する連鎖移動剤としては、オクチルメルカプタン、ノニルメルカプタン、デシルメルカプタン、ドデシルメルカプタン等のアルキルメルカプタン類、チオグリコール酸オクチル、チオグリコール酸ノニル、
チオグリコール酸−２−エチルヘキシル、β−メルカプトプロピオン酸−２−エチルヘキシル等のチオグリコール酸エステル類、２，４−ジフェニル−４−メチル−１−ペンテン、１−メチル−４−イソプロピリデン−１−シクロヘキセン等を挙げることができる。特に、チオグリコール酸エステル類、２，４−ジフェニル−４−メチル−１−ペンテン、１−メチル−４−イソプロピリデン−１−シクロヘキセンを使用した場合には、得られる共重合体が低臭気となり好ましい。なお、連鎖移動剤の使用量は、重合させる全モノマーの０．００１〜３重量％程度の範囲で調節される。なお、重合反応は、通常６０〜１００℃の温度条件下、２〜８時間かけて行われる。さらに、増粘剤、濡れ剤、レベリング剤、消泡剤等を適宜添加することができる。
【００３５】
なお、上記の方法で得られた共重合体は、その共重合体中のカルボン酸を、例えば水酸化ナトリウム、水酸化カリウム、アンモニア、各種の第１級、第２級、第３級アミン等の適当なアルカリ性物質で中和することもできる。また中和すると共重合体の機械安定性が向上するので好ましい。
【００３６】
共重合体のガラス転移温度は、−６０〜−３０℃の範囲のものであり、目的に応じて適宜選択される。因みに、共重合体のガラス転移温度が−６０℃未満になると、得られる皮膜の凝集力が不十分となり、逆に−３０℃を越えると、得られる共重合体の皮膜が硬くなり過ぎて、実用性に乏しくなる傾向がある。
また、必要に応じて一般のロジン系、テルペン系、石油系等のタッキファイヤーを添加してもかまわない。
【００３７】
ここで上記各モノマーの役割について簡単に説明をすると、粘着剤の水に対する膨潤率及び可溶分を高め、さらには粘着剤皮膜の破断強度を弱める成分としては、（ａ）（ポリ）エチレングリコール（メタ）アクリレートモノマーが特に重要であり、また（ｃ）エチレン性不飽和カルボン酸含有モノマーについても重要である。次に粘着剤の粘着性を付与する成分としては、（ｂ）（メタ）アクリル酸のＣ₄ 〜Ｃ₁₈アルキルエステルモノマーが重要であり、更に粘着剤の凝集力を付与する成分としては、（ｃ）エチレン性不飽和カルボン酸含有モノマー及び（ｄ）上記ａ，ｂ及びｃと共重合可能なモノマーが重要である。従ってこれらモノマーをバランスよく重合することが重要となる。
【００３８】
次に粘着シートの構成する表面基材としては、例えばフィルム（セロハン、ポリエチレン、ポリプロピレン、軟質ポリ塩化ビニル、硬質ポリ塩化ビニル、ポリエステル等）、紙（上質紙、アート紙、コート紙、キャスト紙、箔紙、クラフト紙、含浸紙、蒸着紙、低サイズ紙、水溶紙等）、金属フォイル類、合成紙等の支持体や、更にこれらに感熱記録層、熱転写記録用受像層、インクジェット記録用受容層、各種印刷層、着色層、隠蔽層等の層を設けたものなどが適宜使用できる。
【００３９】
粘着シートのリサイクル適性を考慮すると、紙類や、ポリビニルアコール、カルボキシメチルセルロース、メチルセルロース等の水溶性高分子より成形した水溶性フィルム、或いはアルカリ水等に溶解または分散するフィルムを表面基材として使用することが望ましい。
【００４０】
なお、上記紙類の中でも原紙中に、或いは塗被層中にカルシウムが存在すると、経時的または高湿度条件下に保存した場合に接着性能の低下が見られるので、カルシウムが含有しないように調製することが望ましく、例えばアート紙、コート紙、キャスト紙等の紙の表面に顔料を主成分とした顔料塗被層を設けた表面基材を用いる場合には、使用する顔料中にカルシウムを含有しない鉱物質顔料、例えばカオリン、クレー、タルク、焼成カオリン、デラミカオリン、二酸化チタン、水酸化アルミニウム、シリカ、ホワイトカーボン等、あるいはポリスチレン樹脂微粒子、尿素−ホルマリン樹脂微粒子、微小中空粒子等の有機合成顔料等から選択することにより、安定した接着性能を有する粘着シートが得られるので好ましい。因みに、重質炭酸カルシウム、軽質炭酸カルシウム、サチンホワイト等のカルシウムを含む鉱物質顔料を用いてた場合、鉱物質顔料中のカルシウムがカルシウムイオンとなり、基紙を通過し、多量のカルボン酸を含んだ酸性度の高い粘着剤層へ移行することによって、カルシウムイオンとカルボン酸との金属架橋反応を生じてしまい、接着性能が低下してしまうためと推定される。
【００４１】
なお、上記顔料塗被層を設ける場合には、顔料塗被液に、顔料以外に顔料同士および顔料と基材の表面とを固着させるために接着剤を使用する。かかる接着剤としては、例えばカゼイン、デキストリン、澱粉、カルボキシメチルセルロース、メチルセルロース、エチルセルロース、ヒドロキシエチルセルロース、ポリビニルアルコール、スチレン−ブタジエン共重合体、メチルメタクリレート−ブタジエン共重合体、エチレン−塩化ビニル共重合体、エチレン−酢酸ビニル共重合体、アクリル酸エステル共重合体等の天然、または合成の接着剤が水溶液、または水分散液（エマルジョン）の形で使用される。なお、顔料塗被液にはこれら顔料や接着剤の他に、その性質を阻害しない範囲で、消泡剤、分散剤、染料等を必要に応じて、種々の助剤を添加することもできる。
【００４２】
そして、かかる顔料塗被液は、ブレードコーター、バーコーター、エアーナイフコーター、グラビアコーター、ロールコーター、ダイコーター、リップコーター等の通常の塗被装置で塗被される。この場合の塗被量は、固形分重量で２ｇ／ｍ² 以上、好ましくは５〜３０ｇ／ｍ² の範囲で調節される。
【００４３】
なお、粘着シートの形成方法は、通常、剥離シートの剥離剤表面上に粘着剤を塗被、乾燥して粘着剤層を設け、次いで、表面基材とを貼り合わせて仕上げられるが、直接表面基材に塗被して粘着剤層を設けても構わない。
【００４４】
剥離シートとしては、グラシン紙の如き高密度原紙、クレーコート紙、クラフト紙または上質紙等に、例えばカゼイン、デキストリン、澱粉、カルボキシメチルセルロース、メチルセルロース、エチルセルロース、ヒドロキシエチルセルロース、ポリビニルアルコール、スチレン−ブタジエン共重合体、メチルメタクリレート−ブタジエン共重合体、エチレン−塩化ビニル共重合体、エチレン−酢酸ビニル共重合体、アクリル酸エステル共重合体等の天然、または合成樹脂と顔料とを主成分とした目止め層を設けたシート、クラフト紙または上質紙等にポリエチレン等をラミネートしたラミネート紙（ポリラミ紙）、ポリプロピレン等のフィルム等のシートに、水、溶剤型あるいは無用剤型のシリコーン樹脂やフッ素樹脂等を乾燥重量で０．０５〜３ｇ／ｍ² 程度塗被後、熱硬化、電子放射線硬化等によって剥離層を形成したものが使用される。
【００４５】
特に、剥離シートも含んだ粘着シートの構成でのリサイクル適性を考慮すると、上記剥離基材の中で、クレーコート紙、クラフト紙または上質紙等に、例えばカゼイン、デキストリン、澱粉、カルボキシメチルセルロース、メチルセルロース、エチルセルロース、ヒドロキシエチルセルロース、ポリビニルアルコール、スチレン−ブタジエン共重合体、メチルメタクリレート−ブタジエン共重合体、エチレン−塩化ビニル共重合体、エチレン−酢酸ビニル共重合体、アクリル酸エステル共重合体等の天然、または合成樹脂と鉱物質顔料とを主成分とした離解性のある目止め層を乾燥重量で０．１〜１０ｇ／ｍ² 程度設けた剥離基材、または、フィルムではポリビニルアコール、カルボキシメチルセルロース、メチルセルロース等の水溶性高分子より成形した水溶性フィルム、或いはアルカリ水等に溶解または分散するフィルムの基材からなる剥離基材が望ましい。
【００４６】
粘着剤を塗被する塗被装置としては、例えばロールコーター、ナイフコーター、バーコーター、ダイコーター、コンマコーター、リップコーター、グラビアコーター等が適宜使用される。そして、粘着剤の塗被量は、乾燥重量で５〜５０ｇ／ｍ² 程度の範囲で調節される。因みに、５ｇ／ｍ² 未満では、得られる粘着シートの接着性能が不十分となり、一方、５０ｇ／ｍ² を越えると粘着シートの貼り合わせ時に粘着剤がはみ出したり、剥離時に凝集破壊の原因となる恐れがある。
【００４７】
【実施例】
以下に実施例を挙げて本発明をより具体的に説明するが、勿論本発明はそれらに限定されるものではない。尚、例中の部、重量、割合、塗被量等は特に断らない限り、全て固形分重量で示すものである。
【００４８】
実施例１
（カルボン酸変性ロジンエステルの合成）
攪拌機、排気管、滴下ロート、窒素吸入管、温度計を付帯したフラスコにメタクリル酸を７０部とエピクロルヒドリン９０部を仕込み、窒素ガス下で１００℃に昇温して２時間保った。次いで十分に溶解させたアビエチン酸ロジンを、３００部添加し、２３０℃で２時間保った。次いで無水グルタル酸１２５部を添加し、２３０℃で２時間保ち〔化３〕に示すカルボン酸変性ロジンエステルを合成した。
【００４９】
【化３】

【００５０】
（粘着剤の製造）
まず乳化モノマー混合液として、
フェノキシポリエチレングリコールアクリレート（分子量４１２）：１７部
アクリル酸ブチル：７０部
アクリル酸：５部
メタアクリル酸メチル：３部
〔化３〕に示されるカルボン酸変性ロジンエステル：５部
（以上、モノマーの全固形分量を１００部とする）
アニオン系乳化剤（商品名：エマールＮＣ−３５／花王社製）：１．５部
イオン交換水：５０部
を混合して、調製した。
【００５１】
次に攪拌機、クーラー、滴下ロート、窒素吸入管、温度計を付帯したフラスコに、イオン交換水５０部、過酸化カリウム０．５部、オクチルメルカプタン１部を仕込み、窒素置換しながら８０℃に昇温した後、上記乳化モノマー混合液を１／６滴下した。反応率が９０％に達した時点で、残りの乳化モノマー混合液を３時間かけて滴下して重合を行なった。滴下終了後、８０℃で３時間熟成して反応を完結させた。次にフラスコ内容物を４０℃に冷却し、アンモニア水を添加して中和反応を行い反応終了後に強攪拌して粘着剤を製造した。
【００５２】
（剥離シートの作成）
塗被液として、カオリン（商品名：ＵＷ−９０／ＥＭＣ社製）：１５部、リン酸エステル化澱粉（商品名：ニ−ルガムＡ−５５Ｃ／アベベ社製）：５部、ポリビニルアルコール（商品名：クラレＰＶＡ−１０３／クラレ社製）：８０部、分散剤（商品名：アロンＡ−９／東亞合成化学工業社製）：０．１部から成る組成物を、固形分濃度が４０％となるように混合調製して市販の米坪６４ｇ／ｍ² の上質紙の上に乾燥重量が５ｇ／ｍ² となるように塗被、乾燥して目止め層を設けた。次いで、スーパーキャレンダーにて平滑仕上げを行い、剥離基材を得た。
【００５３】
次に、かくして得られた剥離基材の目止め層上に溶剤型のシリコーン剥離剤（商品名：ＬＴＣ−３００Ｂ／東レ・ダウコーニング社製）：１００部、触媒（商品名：ＳＲＸ−２１２／東レ・ダウコーニング社製）：０．８部を乾燥重量が１．０ｇ／ｍ² となるように塗被、熱硬化して剥離シートを得た。
【００５４】
（粘着シートの作成）
上記の方法で得られた剥離シートに、上記粘着剤を関そう重量で２５ｇ／ｍ²となるように塗被、熱硬化した後、市販の米坪６４ｇ／ｍ²の上質紙と貼り合せて、粘着シートを得た。
【００５５】
参考実施例１
（粘着剤の製造）
乳化モノマー混合液として、
フェノキシポリエチレングリコールアクリレート（分子量４１２）：４０部
アクリル酸ブチル：４５部
アクリル酸：５部
〔化３〕に示されるカルボン酸変性ロジンエステル：５部
（以上、モノマーの全固形分量を１００部とする）
アニオン系乳化剤（商品名：エマールＮＣ−３５／花王社製）：１．５部
イオン交換水：５０部 を混合して調製したこと以外は実施例１と同様にして粘着剤を得た。
【００５６】
（粘着シートの作成）
前記粘着剤を使用した以外は、実施例１と同様にして粘着シートを得た。
【００５７】
参考実施例２
（粘着剤の製造）
乳化モノマー混合液として、
メトキシポリエチレングリコールメタクリレート（分子量２９３）：５部
アクリル酸ブチル：８０部
アクリル酸：２部
メタクリル酸メチル：８部
〔化３〕に示されるカルボン酸変性ロジンエステル：５部
（以上、モノマーの全固形分量を１００部とする）
アニオン系乳化剤（商品名：エマールＮＣ−３５／花王社製）：１．５部
イオン交換水：５０部
を混合して調製したこと以外は実施例１と同様にして粘着剤を得た。
【００５８】
（粘着シートの作成）
前記粘着剤を使用した以外は、実施例１と同様にして粘着シートを得た。
【００５９】
比較例１
（粘着剤の製造）
乳化モノマー混合液として、
フェノキシポリエチレングリコールクリレート（分子量４１２）：３部 アクリル酸ブチル：８０部
アクリル酸：８部
メタクリル酸メチル：４部
〔化３〕に示されるカルボン酸変性ロジンエステル：５部
（以上、モノマーの全固形分量を１００部とする）
アニオン系乳化剤（商品名：エマールＮＣ−３５／花王社製）：１．５部
イオン交換水：５０部
を混合して調製したこと以外は、実施例１と同様にして粘着剤を得た。
【００６０】
（粘着シートの作成）
前記粘着剤を使用した以外は、実施例１と同様にして粘着シートを得た。
【００６１】
比較例２
（粘着剤の製造）
乳化モノマー混合液として、
アクリル酸ブチル：７０部
アクリル酸：５部
メタクリル酸メチル：２５部
（以上、モノマーの全固形分量を１００部とする）
アニオン系乳化剤（商品名：エマールＮＣ−３５／花王社製）：１．５部
イオン交換水：５０部
を混合して調製したこと以外は、実施例１と同様にして粘着剤を得た。
【００６２】
（粘着シートの作成）
前記粘着剤を使用した以外は、実施例１と同様にして粘着シートを得た。
【００６３】
（粘着シートの作成）
前記粘着剤として、市販の汎用タイプのアクリル酸エステル系粘着剤（商品名：Ｌ−１４５／日本カーバイド社）を使用した以外は、実施例１と同様にして粘着シートを得た。
【００６４】
以上のようにして作成した粘着剤および粘着シートについて、下記の測定および評価を行い、得られた結果を表１に示した。
【００６５】
＜測定項目＞
〔水膨潤率〕
粘着剤層の水に対する膨潤率を下記の方法で測定した。
表面基材に市販のポリエステルフィルム（厚み５０μｍ）を、また剥離紙に市販のポリエチレンラミネート剥離紙を用いて粘着剤を乾燥重量で２５ｇ／ｍ² になるようにして粘着シートを作成した。その後剥離紙を除去して、ポリエステルフィルム、粘着剤層の積層体を２０℃の水道水に１時間浸漬する。水浸漬の前後での粘着剤皮膜の厚みをそれぞれ測定し、下記計算式に従って膨潤率を求めた。（単位：％）
【００６６】
【数３】

【００６７】
〔水可溶分率〕
粘着剤皮膜の水可溶成分含有率（水可溶分率）を下記の方法で測定した。
表面基材に市販のポリエステルフィルム（厚み５０μｍ）を、また剥離紙に市販のポリエチレンラミネート剥離紙を用いて各粘着剤を乾燥重量で２５ｇ／ｍ² になるようにして粘着シートを作成した。その後剥離紙を除去してポリエステルフィルム、粘着剤層の積層体を２０℃の水道水に２４時間浸漬する。その後超音波により粘着剤をポリエステルフィルムから完全に除去し粘着剤分散液を作る。その粘着剤分散液をガラスフィルターで濾過し、その粘着剤の濾過重量と、また濾過水を乾燥させて水に溶けだした糊の重量を測定し、下記計算式に従って水可溶分率を求めた。（単位：％）
【００６８】
【数４】

【００６９】
〔破断強度〕
粘着剤皮膜の水中での破断強度を、下記の方法で測定した。
先ず、ポリエチレンラミネート紙に溶剤型の重剥離型シリコーン剥離剤（商品名：ＬＴＣ−３５０Ａ／東レ・ダウコーニング社製）：１００部、触媒（商品名：ＳＲＸ−２１２／東レ・ダウコーニング社製）：０．８部を乾燥重量が０．５ｇ／ｍ² となるように塗被、熱硬化して剥離シートＡを作成し、また軽剥離型シリコーン剥離剤（商品名：ＬＴＣ−３００Ｂ／東レ・ダウコーニング社製）を用いること以外は上記剥離シートＡの作成方法と同様にして剥離シートＢを作成する。次に剥離シートＡ、粘着剤層、剥離シートＢとを順次積層して粘着シートを作成する。この場合の各粘着剤層の塗布量は乾燥重量で１００ｇ／ｍ² になるようする。
【００７０】
次に上記の方法で得られた粘着シートを巾２０ｍｍ、長さ１２０ｍｍの形に切断し、さらに剥離シートＡ及び剥離シートＢを剥がし粘着剤層の試験片を作る。得られた試験片を水に浸漬して１時間後に、ＪＩＳＫー６３０１の引張り強さの測定方法に準拠して粘着剤層皮膜の切断に至る最大荷重を測定し、下記計算式により破断強度をもとめた。（単位：kgf/cm² ）
【００７１】
【数５】

なお、粘着剤層試験片の厚みは下記方法で測定できる。
粘着剤層の厚み＝粘着シートの厚み−｛剥離シートＡの厚み＋剥離シートＢの厚み｝
【００７２】
＜評価項目＞
〔接着力〕
ＪＩＳ−Ｚ−０２３７の常態粘着力の測定方法に準拠して、接着力を測定した（単位：ｇ／２５ｍｍ）。
【００７３】
〔凝集力〕
ＪＩＳ−Ｚ−０２３７の常態保持力の測定方法に準拠して、凝集力を測定した。そして測定結果に応じて下記評価基準に従い判定した。
◎：測定開始後６０分の間では重りの落下がなかった。
○：測定開始後５分から６０分の間で重りが落下した。
×：測定開始後５未満の間で重りが落下した。
【００７４】
〔リサイクル適性〕
粘着シート５０ｇに対し、パルプ濃度が３％になるように水を加え、ＴＡＰＰＩ離解機にて１５００００回転処理した後、パルプ濃度が１５％になるまで脱水し、１８％濃度のＮａＯＨ水溶液を１．５ｇ、脱墨剤（商品名ＤＩ−６００／花王社製）１０％濃度溶液を１．８ｇをそれぞれ添加し、４０℃で２０分間放置し、次にパルプ濃度が２５％になるなで脱水し、１８％濃度のＮａＯＨ水溶液を３．６２ｇ、３０％濃度のＮａ2 ＳｉＯ3 水溶液を３．８５ｇ、６％濃度のＨ2 Ｏ2 水を５ｇをそれぞれ添加し、次いで双腕式ニーダーで５分間ニーディング処理を行った。
【００７５】
次に５５℃に保ちながら１２０分間放置した後、パルプ濃度が１７．５％になるまで水で希釈し、次いで２回目のニーディング処理を同様に行った。その後更にパルプ濃度が１％いなるまで水で希釈した。次にこの１％濃度のパルプ分散液をフローテーターにて１０分間浮上分離処理を行った。その際発生する泡をスクレーパーにて取り除いて得られた浮上分離処理液を更に水８００ｍｌで洗浄し、１３％濃度になるまで脱水した。このようにして得られたパルプ分散液を０．３％濃度になるまで水を加えて手抄きシートを作成し、未離解物の残存状態を目視し下記評価基準にて判定した。
【００７６】
（リサイクル適性評価基準）
◎：粘着剤異物が全くない。
○：数ミクロン程度の粘着剤異物がほんの僅かにあるが、実用上問題ない。
△：１ミリ以上の粘着剤異物はないが、数ミクロン程度の粘着剤異物が目立ち
実用上問題となる。
×：１ミリ以上の粘着剤異物がかなり目立つ。
【００７７】
〔総合評価〕
上記の各評価を総合して本発明のリサイクル可能な粘着シートとしての性能を評価した。
○：粘着シートとして古紙リサイクルが可能であり、且つその粘着性能においても実用上問題のないものである。
×：粘着シートとして古紙リサイクルが不可能である。または、古紙リサイクルは可能であってもその粘着性能が劣り実用上問題がある。
【００７８】
【表１】

【００７９】
【発明の効果】
表１の結果から明らかなように、本発明の粘着シートは、その粘着剤層が水に馴染みやすく、さらに水浸漬後に皮膜強度が脆くなるという性質を備えていることにより、古紙リサイクルする際の離解工程にて容易に粘着剤層を微粒子状に変化させることができ、精選、粗選、フローテイション等の各工程で容易にパルプ分から除去できるため、パルプのリサイクル適性が優れており、且つその接着性能にのおいても十分に使用可能な粘着シートであった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive sheet. Specifically, the present invention relates to a recyclable adhesive sheet.
[0002]
[Prior art]
Adhesive sheets are widely used in the form of labels, stickers, emblems, delivery slips, etc. for commercial use, office use, process control use, logistics management use, home use use and the like.
The general structure of this pressure-sensitive adhesive sheet will be described. A pressure-sensitive adhesive layer is provided on a surface base material, and a release sheet is laminated to protect the pressure-sensitive adhesive layer. Paper, foil, film or the like is used as the surface substrate. Also, as release sheets, high-density base paper such as glassine paper, clay-coated paper, polylaminate base paper in which a resin film such as polyethylene is laminated on kraft paper or high-quality paper, or polyvinyl alcohol, starch, etc. on craft paper or high-quality paper A resin coating base paper or the like provided with a coating layer mainly composed of a water-soluble polymer or the like and a pigment is applied with a release agent such as a silicone compound or a fluorine compound.
Further, as the pressure-sensitive adhesive, rubber-based, acrylic-based, vinyl ether-based emulsions, solvents or various non-solvent pressure-sensitive adhesives are used.
[0003]
On the other hand, with regard to waste paper recycling, the amount of waste paper used, including waste paper for recycling, currently exceeds 50% of paper and paperboard production raw materials in Japan, and has already occupied the position of main raw materials. It is up to.
Recycled pulp can be used in newspapers, cardboard, magazines, imitations, colors (including art), whites, cards, white, medium white, white Manila, tickets, medium-recycled old, tea imitation paper (Western) ), Mounts, land tickets, balls, thermal recording paper, pressure-sensitive copying paper, OCR paper, and the like.
[0004]
The recycled pulping method from these waste papers generally includes a disaggregation step of disaggregating the waste paper to obtain a pulp suspension, a rough selection step for separating foreign matter in the pulp suspension, a selection step, and a removal step for separating the printing ink. Regenerated pulping is carried out through a black ink process, a bleaching process for whitening the color, and the like.
[0005]
However, wax-treated paper, pressure-sensitive adhesive sheets, and the like cannot be separated into water-insoluble wax, pressure-sensitive adhesive, and the like from pulp fibers, and are regarded as waste paper that cannot be recycled. In particular, in the case of the pressure-sensitive adhesive label, 5 to 50% of water-insoluble pressure-sensitive adhesive is contained. Further, since this pressure-sensitive adhesive has strong adhesive force, it cannot be separated from pulp fibers.
Also, when paper is made using the recycled pulp while the recycled pulp is still contained in the recycled pulp, the pressure-sensitive adhesive closes the eyes of the wire in the paper making process, or the press roll or blanket is soiled, causing paper breakage. There arises a problem that the efficiency is remarkably lowered and a problem that the paper layer formation or the quality is adversely affected such as the formation of spots on the paper surface.
In addition, since it is usually in a state where release papers having poor disaggregation properties such as the above-described polylaminate paper are stacked, it is more difficult to regenerate pulping.
Because of these problems, the actual situation is that recycled pulp from adhesive sheet waste paper is currently avoided and has become industrial waste.
[0006]
Recently, due to problems such as forest resources and the environment, several cases have been reported in which the adhesive sheet that cannot be recycled as described above has been successfully recycled by physically or deviceally devising it. For example, as disclosed in Japanese Patent Laid-Open No. 4-174787, an inorganic pigment is added to the disaggregation process to eliminate the adhesiveness of the paste, and the screen treatment after disaggregation as disclosed in Japanese Patent Laid-Open No. 4-163383. There are methods for removing the paste by finely reducing the paste, and all of them are special treatment methods, which are different from ordinary regenerated pulping steps.
[0007]
[Problems to be solved by the invention]
In the present invention, when the recycled pulp is obtained from the waste paper of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer can be easily disaggregated without causing adverse effects by making the pressure-sensitive adhesive layer excellent in re-disaggregation with respect to water. An object of the present invention is to provide a pressure-sensitive adhesive sheet having re-disintegrating properties that can regenerate pulp in a normal regenerated pulping process without contaminating water.
[0008]
[Means for Solving the Problems]
In order to solve such problems, the present inventors have conducted intensive research on the relationship between the physical properties of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet and the suitability of used paper processing. In order to obtain recycled pulp from the waste paper of the pressure-sensitive adhesive sheet, it is necessary to remove the pressure-sensitive adhesive component in each step such as rough selection, selection, and flotation, which are subsequent steps of the disaggregation step. For that purpose, it is necessary to change the pressure-sensitive adhesive layer into an optimum shape for removal in each step, that is, to change it into fine particles having a particle diameter of about 1 mm or less. For this purpose, in the disaggregation process in which a large amount of water is added to the used paper and stirred at high speed, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet can be easily separated from the pressure-sensitive adhesive sheet base material by mechanical and physical action, Furthermore, the present inventors have found that it is necessary to easily change the pressure-sensitive adhesive layer film into fine particles.
[0009]
In order to obtain a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer can be changed into fine particles by such a disaggregation process, as a result of repeated research, a pressure-sensitive adhesive whose swelling ratio with respect to water exceeds a specific value is obtained. It has been found that the pressure-sensitive adhesive layer can be easily separated from the surface base material when used.
(1). The present invention is a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive sheet having a surface base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a water swelling ratio of 50% or more.
[0010]
Furthermore, as a result of repeated researches by the inventors, it has been found that those having a water-soluble component content satisfying a specific condition can be very easily formed into fine particles.
(2). The pressure-sensitive adhesive sheet according to (1), wherein the content of the water-soluble component in the pressure-sensitive adhesive layer is 3 to 40%.
[0011]
It was also found that fine particles can be efficiently formed by using a pressure-sensitive adhesive whose breaking strength after immersion in water is a specific value or less.
(3). The breaking strength after immersion in water is 2kgf / cm²The pressure-sensitive adhesive sheet according to (1) or (2), which uses the following pressure-sensitive adhesive.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The swelling ratio of the pressure-sensitive adhesive referred to in the present invention is a value determined as follows.
A commercially available polyester film (50 μm) is used for the surface substrate, a commercially available polyethylene laminate release paper is used for the release paper, and the adhesive is 25 g / m in dry weight.²An adhesive sheet is prepared by providing Thereafter, the laminate of the polyester film and the pressure-sensitive adhesive layer obtained by removing the release paper is immersed in tap water at 20 ° C. for 1 hour. The thickness of the pressure-sensitive adhesive film before and after immersion in water is measured, and the swelling rate is obtained according to the following formula. (unit:%)
[0013]
[Expression 1]

[0014]
In the present invention, it is necessary to use an adhesive having a swelling rate of 50% or more. Incidentally, when the swelling rate of the pressure-sensitive adhesive layer with respect to water is less than 50%, the pressure-sensitive adhesive component cannot be sufficiently separated from the pulp because the pressure-sensitive adhesive layer does not swell sufficiently in the disaggregation process. Yes, as a result, the residual ratio of the pressure-sensitive adhesive component in the recycled pulp becomes high.
[0015]
  Even if the pressure-sensitive adhesive satisfying such a swelling rate is used, the content of the water-soluble component in the pressure-sensitive adhesive layer is further 3 to 40%.ThisWhen the pressure-sensitive adhesive layer is immersed in water, the penetration of water into the pressure-sensitive adhesive layer is good and the pressure-sensitive adhesive layer partially dissolves in water, so the pressure-sensitive adhesive layer film is brittle It can be easily changed to fine particles by a large stirring force in the disaggregation process, and it is possible to remove the adhesive component in each process such as rough selection, fine selection, and flotation, which are subsequent processes of the disaggregation process. This is preferable. Incidentally, when the water-soluble component in the pressure-sensitive adhesive layer is less than 3%, the water permeability to the pressure-sensitive adhesive layer is inferior. On the other hand, when it exceeds 40%, the cohesive strength of the pressure-sensitive adhesive is high in terms of pressure-sensitive adhesive properties. It becomes scarce and impractical.
[0016]
Furthermore, in order to easily change the pressure-sensitive adhesive layer film into fine particles in the used paper disaggregation process, the breaking strength of the pressure-sensitive adhesive layer after water immersion is 2 kgf / cm.²The following is more preferable. Incidentally, the breaking strength of the adhesive layer after immersion in water is 2 kgf / cm.²If it exceeds 1, the pressure-sensitive adhesive layer film cannot be made into fine particles in the disaggregation step, and it is insufficient to remove the pressure-sensitive adhesive component in each step such as rough selection, fine selection and flotation, which are subsequent steps of the disaggregation step As a result, the residual ratio of the pressure-sensitive adhesive component in the recycled pulp becomes high.
[0017]
In addition, the breaking strength after water immersion of an adhesive is the value calculated | required as follows.
First, two kinds of release sheets having different release weights using a polyethylene laminated paper as a base material are prepared. One side of this release sheet has a coating weight of 100 g / m in dry weight.²Then, the pressure-sensitive adhesive layer is formed so that the other release sheet is laminated. That is, it is set as the structure of release sheet A / adhesive layer / release sheet B.
Next, the obtained pressure-sensitive adhesive sheet is cut into a shape having a width of 20 mm and a length of 120 mm, and the release sheet A and the release sheet B are further peeled to make a test piece of the pressure-sensitive adhesive layer. One hour after immersing the obtained test piece in water, the maximum load leading to the cutting of the pressure-sensitive adhesive layer film was measured in accordance with the tensile strength measurement method of JIS-K-6301. Find strength. (Unit: kgf / cm²)
[0018]
[Expression 2]

[0019]
Examples of the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer satisfying the above conditions include a (meth) acrylic acid ester copolymer containing a (poly) ethylene glycol (meth) acrylate monomer as an essential component, such as the following monomer composition. A pressure-sensitive adhesive sheet using a polymer may be one preferred form of the pressure-sensitive adhesive sheet excellent in re-disintegration property of the present invention.
[0020]

[0021]
The (a) (poly) ethylene glycol (meth) acrylate monomer is a compound represented by the general formula as shown in [Chemical Formula 1].
[0022]
[Chemical 1]

[0023]
(Here, R₁Is a methyl group or a hydrogen atom, and R₂Represents a methyl group or a phenyl group, respectively. In addition, m is an integer of 1-10. )
[0024]
These (a) (poly) ethylene glycol (meth) acrylate monomers need to be copolymerized in the range of 5 to 40% by weight. Incidentally, if it is less than 5% by weight, the water re-disintegration property is insufficient. On the other hand, if the blending ratio of these hydrophilic monomers increases, the hydrophilicity of the pressure-sensitive adhesive film increases and the disaggregation improves, but if it exceeds 40% by weight, the cohesive force of the pressure-sensitive adhesive decreases and the function of the pressure-sensitive adhesive sheet decreases. .
[0025]
(B) C of (meth) acrylic acid_Four~ C₁₈Examples of the alkyl ester monomer include butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, (2-ethylhexyl (meth) acrylate), stearyl (meth) acrylate, and the like. The proportion of these monomers in the copolymer portion is copolymerized in the range of 20 to 80% by weight. Incidentally, if it is less than 20% by weight, the adhesive strength of the pressure-sensitive adhesive is poor, and if it exceeds 80% by weight, water re-disintegration becomes insufficient.
[0026]
Examples of the (c) ethylenically unsaturated carboxylic acid-containing monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, monoalkylmaleic acid, monoalkylitaconic acid, and monoalkylfumaric acid. It is done. And the ratio which occupies for the copolymer part of these monomers is copolymerized in the range of 0-20 weight%. Incidentally, if it exceeds 20% by weight, the adhesive strength of the adhesive becomes insufficient.
[0027]
Furthermore, (a) (poly) ethylene glycol (meth) acrylate monomer, (b) (meth) acrylic acid C_Four~ C₁₈Examples of other monomers copolymerizable with alkyl ester monomers and (c) ethylenically unsaturated carboxylic acid-containing monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Cyclohexyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, glycidyl (meth) acrylate, vinyl acetate, Vinyl propionate, vinyl chloride, vinylidene chloride, styrene, divinylbenzene, ethylene, (meth) acrylonitrile, (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N′-methylenebis (meth) acrylamide, and for example: of Carboxylic acid-modified rosin ester monomers represented by the general formula [Formula 2] and the like.
[0028]
[Chemical 2]

[0029]
(Wherein R_ThreeRepresents a hydrogen atom or a methyl group, and n represents an integer of 1 to 8. )
[0030]
And the ratio of these monomers to a copolymer is adjusted in the range of 1 to 40 weight%. Incidentally, if it is less than 1% by weight, the pressure-sensitive adhesive becomes too soft. On the other hand, if it exceeds 40% by weight, the pressure-sensitive adhesive becomes too hard and the function of the pressure-sensitive adhesive sheet is deteriorated.
[0031]
Among these other copolymerizable monomers, methyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, glycidyl (meth) acrylate, divinylbenzene, (meth) acrylonitrile, (meth) acrylamide N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N′-methylenebis (meth) acrylamide, carboxylic acid-modified rosin ester monomer represented by [Chemical Formula 2] and the like have a glass transition temperature, This is preferable from the standpoint of adhesive performance.
[0032]
The method for producing the copolymer is not particularly limited. For example, a solution polymerization method in the presence of water, a solvent, a chain transfer agent, a polymerization initiator, an emulsifier, a chain transfer agent, or the like. , By emulsion polymerization in an aqueous system in the presence of a polymerization initiator, a dispersant and the like.
[0033]
The monomer concentration during the polymerization is usually 30 to 70% by weight, preferably about 40 to 60% by weight. Examples of the polymerization initiator used in the polymerization include persulfates such as potassium persulfate and ammonium persulfate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4 -Initiation of so-called redox polymerization consisting of azo compounds such as (dimethylvaleronitrile), peroxides such as hydrogen peroxide, benzoyl peroxide, lauryl peroxide, ammonium persulfate and sodium sulfite, acidic sodium sulfite, etc. Agents and the like.
The usage-amount of the said polymerization initiator is 0.2-2 weight% with respect to the monomer whole quantity normally used for superposition | polymerization, More preferably, it adjusts in the range of 0.3-1 weight%.
[0034]
Furthermore, as a chain transfer agent to be added during copolymerization, alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, octyl thioglycolate, nonyl thioglycolate,
Thioglycolic acid esters such as thioglycolic acid-2-ethylhexyl, β-mercaptopropionic acid-2-ethylhexyl, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1- And cyclohexene. In particular, when thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, and 1-methyl-4-isopropylidene-1-cyclohexene are used, the resulting copolymer has a low odor. preferable. In addition, the usage-amount of a chain transfer agent is adjusted in the range of about 0.001 to 3 weight% of all the monomers to superpose | polymerize. The polymerization reaction is usually performed at a temperature of 60 to 100 ° C. over 2 to 8 hours. Furthermore, a thickener, a wetting agent, a leveling agent, an antifoaming agent, etc. can be added suitably.
[0035]
In addition, the copolymer obtained by the above-described method is obtained by using carboxylic acid in the copolymer, for example, sodium hydroxide, potassium hydroxide, ammonia, various primary, secondary, and tertiary amines. It is also possible to neutralize with a suitable alkaline substance. Neutralization is preferable because the mechanical stability of the copolymer is improved.
[0036]
The glass transition temperature of the copolymer is in the range of −60 to −30 ° C., and is appropriately selected according to the purpose. Incidentally, when the glass transition temperature of the copolymer is less than −60 ° C., the cohesive force of the resulting film becomes insufficient, and conversely, when it exceeds −30 ° C., the resulting copolymer film becomes too hard, There is a tendency to become less practical.
Moreover, you may add tackifiers, such as a general rosin type, a terpene type, and a petroleum type, as needed.
[0037]
Here, the role of each monomer will be briefly described. As a component for increasing the swelling ratio and soluble content of the pressure-sensitive adhesive in water and further reducing the breaking strength of the pressure-sensitive adhesive film, (a) (poly) ethylene glycol A (meth) acrylate monomer is particularly important, and (c) an ethylenically unsaturated carboxylic acid-containing monomer is also important. Next, as a component which gives the adhesiveness of an adhesive, (b) C of (meth) acrylic acid_Four~ C₁₈Alkyl ester monomers are important, and as components that give cohesive strength to the pressure-sensitive adhesive, (c) ethylenically unsaturated carboxylic acid-containing monomers and (d) monomers copolymerizable with a, b and c are important. It is. Therefore, it is important to polymerize these monomers in a balanced manner.
[0038]
Next, examples of the surface base material constituting the pressure-sensitive adhesive sheet include films (cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, etc.), paper (quality paper, art paper, coated paper, cast paper, Foil paper, kraft paper, impregnated paper, vapor-deposited paper, low-size paper, water-soluble paper, etc.), metal foils, supports such as synthetic paper, etc., and thermal recording layer, thermal transfer recording image receiving layer, inkjet recording receiving Those provided with layers such as a layer, various printed layers, a colored layer, and a concealing layer can be used as appropriate.
[0039]
In consideration of the recyclability of the pressure-sensitive adhesive sheet, paper, a water-soluble film formed from a water-soluble polymer such as polyvinyl alcohol, carboxymethyl cellulose, or methyl cellulose, or a film that dissolves or disperses in alkaline water is used as the surface substrate. It is desirable.
[0040]
Among the above papers, if calcium is present in the base paper or in the coating layer, the adhesive performance will deteriorate when stored over time or under high humidity conditions. For example, when using a surface substrate provided with a pigment coating layer mainly composed of pigment on the surface of paper such as art paper, coated paper, cast paper, etc., calcium is contained in the pigment used. Mineral pigments such as kaolin, clay, talc, calcined kaolin, deramikaolin, titanium dioxide, aluminum hydroxide, silica, white carbon, etc., or organic synthetic pigments such as polystyrene resin fine particles, urea-formalin resin fine particles, and fine hollow particles It is preferable to select from such as a pressure-sensitive adhesive sheet having stable adhesion performance. Incidentally, when mineral pigments containing calcium such as heavy calcium carbonate, light calcium carbonate, and satin white are used, the calcium in the mineral pigment becomes calcium ions, passes through the base paper, and contains a large amount of carboxylic acid. However, it is presumed that the transition to the highly acidic pressure-sensitive adhesive layer causes a metal crosslinking reaction between calcium ions and carboxylic acid, resulting in a decrease in adhesion performance.
[0041]
In addition, when providing the said pigment coating layer, an adhesive agent is used in order to fix pigments and the pigment and the surface of a base material other than a pigment in a pigment coating liquid. Examples of such adhesives include casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene. -Natural or synthetic adhesives such as vinyl acetate copolymers and acrylate copolymers are used in the form of aqueous solutions or aqueous dispersions (emulsions). In addition to these pigments and adhesives, various auxiliary agents such as antifoaming agents, dispersants, dyes and the like can be added to the pigment coating solution as long as the properties are not impaired. .
[0042]
Such a pigment coating solution is applied by a normal coating apparatus such as a blade coater, a bar coater, an air knife coater, a gravure coater, a roll coater, a die coater, or a lip coater. The coating amount in this case is 2 g / m in terms of solid content.²Or more, preferably 5 to 30 g / m²Adjusted in the range of.
[0043]
The pressure-sensitive adhesive sheet is usually formed by coating a pressure-sensitive adhesive on the release sheet surface of the release sheet, drying to provide a pressure-sensitive adhesive layer, and then bonding the surface base material to finish. An adhesive layer may be provided by coating on a substrate.
[0044]
Examples of the release sheet include high-density base paper such as glassine paper, clay-coated paper, kraft paper, or high-quality paper. Sealing layer mainly composed of natural or synthetic resin and pigment such as polymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, acrylate ester copolymer Water, solvent-type or useless-type silicone resin or fluororesin is dried on sheets such as laminated paper (polylaminated paper) obtained by laminating polyethylene on kraft paper or high-quality paper, and films such as polypropylene. 0 by weight. 5~3g / m²After coating to a certain extent, a layer having a release layer formed by heat curing, electron radiation curing or the like is used.
[0045]
In particular, in consideration of the recyclability in the configuration of the pressure-sensitive adhesive sheet including the release sheet, among the above release substrates, for example, casein, dextrin, starch, carboxymethylcellulose, methylcellulose, etc. Natural, such as ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, acrylate copolymer, Alternatively, a disintegrating sealing layer mainly composed of a synthetic resin and a mineral pigment is 0.1 to 10 g / m in dry weight.²There is a release substrate comprising a release substrate provided to a certain extent, or a water-soluble film formed from a water-soluble polymer such as polyvinyl alcohol, carboxymethyl cellulose, or methyl cellulose, or a film substrate that is dissolved or dispersed in alkaline water or the like. desirable.
[0046]
For example, a roll coater, a knife coater, a bar coater, a die coater, a comma coater, a lip coater, a gravure coater, or the like is appropriately used as a coating apparatus for coating an adhesive. And the coating amount of an adhesive is 5-50 g / m by dry weight.²Adjusted to the extent of the degree. Incidentally, 5g / m²Is less than 50 g / m, the adhesive performance of the resulting pressure-sensitive adhesive sheet is insufficient.²Exceeding this may cause the pressure-sensitive adhesive to protrude when the pressure-sensitive adhesive sheet is bonded, or cause cohesive failure during peeling.
[0047]
【Example】
EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the examples, all parts, weights, ratios, coating amounts, etc. are indicated by solids weight unless otherwise specified.
[0048]
Example 1
  (Synthesis of carboxylic acid-modified rosin ester)
  A flask equipped with a stirrer, an exhaust pipe, a dropping funnel, a nitrogen suction pipe and a thermometer was charged with 70 parts of methacrylic acid and 90 parts of epichlorohydrin, heated to 100 ° C. under nitrogen gas and maintained for 2 hours. Next, 300 parts of fully dissolved rosin abietic acid was added and kept at 230 ° C. for 2 hours. Next, 125 parts of glutaric anhydride was added and maintained at 230 ° C. for 2 hours to synthesize carboxylic acid-modified rosin ester shown in [Chemical Formula 3].
[0049]
[Chemical 3]

[0050]
(Manufacture of adhesives)
First, as an emulsified monomer mixture,
Phenoxypolyethylene glycol acrylate (molecular weight 412): 17 parts
Butyl acrylate: 70 parts
Acrylic acid: 5 parts
Methyl methacrylate: 3 parts
Carboxylic acid-modified rosin ester represented by [Chemical Formula 3]: 5 parts
(The total solid content of the monomer is 100 parts)
Anionic emulsifier (trade name: EMAL NC-35 / manufactured by Kao Corporation): 1.5 parts
Ion exchange water: 50 parts
Were mixed to prepare.
[0051]
  Next, a flask equipped with a stirrer, cooler, dropping funnel, nitrogen suction tube and thermometer was charged with 50 parts of ion exchange water, 0.5 part of potassium peroxide, and 1 part of octyl mercaptan, and the temperature was raised to 80 ° C. while purging with nitrogen. After warming, 1/6 of the emulsion monomer mixture was added dropwise. When the reaction rate reached 90%, the remaining emulsified monomer mixture was added dropwise over 3 hours to carry out polymerization. After completion of the dropping, the reaction was completed by aging at 80 ° C. for 3 hours. Next, the flask contents were cooled to 40 ° C., neutralized by adding aqueous ammonia, and stirred vigorously after the reaction was completed.StickyA dressing was produced.
[0052]
(Creation of release sheet)
As coating solution, kaolin (trade name: UW-90 / EMC): 15 parts, phosphate esterified starch (trade name: Neal Gum A-55C / Abebe): 5 parts, polyvinyl alcohol (product) Name: Kuraray PVA-103 / manufactured by Kuraray Co., Ltd.): 80 parts, dispersant (trade name: Aron A-9 / manufactured by Toagosei Chemical Industry Co., Ltd.): 0.1 part, a solid content concentration of 40% Mix and prepare so that it becomes 64 g / m²5g / m dry weight on high quality paper²It was coated and dried so that a sealing layer was provided. Subsequently, smooth finishing was performed with a super calender to obtain a release substrate.
[0053]
Next, a solvent-type silicone release agent (trade name: LTC-300B / manufactured by Toray Dow Corning): 100 parts, catalyst (trade name: SRX-212 /) on the sealing layer of the release substrate thus obtained. Toray Dow Corning): 0.8 parts dry weight 1.0g / m²Coating and heat curing were performed to obtain a release sheet.
[0054]
(Creation of adhesive sheet)
  The release sheet obtained by the above method has a weight of 25 g / m with respect to the pressure-sensitive adhesive.²After coating and heat-curing so that it becomes²Laminated with high quality paper, StickyA landing sheet was obtained.
[0055]
referenceExample1
(Manufacture of adhesives)
  As an emulsion monomer mixture,
Phenoxypolyethylene glycol acrylate (molecular weight 412): 40 parts
Butyl acrylate: 45 parts
Acrylic acid: 5 parts
Carboxylic acid-modified rosin ester represented by [Chemical Formula 3]: 5 parts
(The total solid content of the monomer is 100 parts)
Anionic emulsifier (trade name: EMAL NC-35 / manufactured by Kao Corporation): 1.5 parts
Ion-exchanged water: other than that prepared by mixing 50 partsIs realSame as Example 1StickyA dressing was obtained.
[0056]
(Creation of adhesive sheet)
    Except for using the adhesive, RealA pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
[0057]
Reference Example 2
(Manufacture of adhesives)
  As an emulsion monomer mixture,
Methoxy polyethylene glycol methacrylate (molecular weight 293): 5 parts
Butyl acrylate: 80 parts
Acrylic acid: 2 parts
Methyl methacrylate: 8 parts
Carboxylic acid-modified rosin ester represented by [Chemical Formula 3]: 5 parts
(The total solid content of the monomer is 100 parts)
Anionic emulsifier (trade name: EMAL NC-35 / manufactured by Kao Corporation): 1.5 parts
Ion exchange water: 50 parts
Other than that prepared by mixingIs realA pressure-sensitive adhesive was obtained in the same manner as in Example 1.
[0058]
(Creation of adhesive sheet)
  Except for using the adhesive, RealA pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
[0059]
Comparative Example 1
(Manufacture of adhesives)
  As an emulsion monomer mixture,
Phenoxypolyethylene glycol acrylate (molecular weight 412): 3 parts Butyl acrylate: 80 parts
Acrylic acid: 8 parts
Methyl methacrylate: 4 parts
Carboxylic acid-modified rosin ester represented by [Chemical Formula 3]: 5 parts
(The total solid content of the monomer is 100 parts)
Anionic emulsifier (trade name: EMAL NC-35 / manufactured by Kao Corporation): 1.5 parts
Ion exchange water: 50 parts
Other than that prepared by mixingIs realA pressure-sensitive adhesive was obtained in the same manner as in Example 1.
[0060]
(Creation of adhesive sheet)
  Except for using the adhesive, RealA pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
[0061]
Comparative Example 2
(Manufacture of adhesives)
  As an emulsion monomer mixture,
Butyl acrylate: 70 parts
Acrylic acid: 5 parts
Methyl methacrylate: 25 parts
(The total solid content of the monomer is 100 parts)
Anionic emulsifier (trade name: EMAL NC-35 / manufactured by Kao Corporation): 1.5 parts
Ion exchange water: 50 parts
Other than that prepared by mixingIs realA pressure-sensitive adhesive was obtained in the same manner as in Example 1.
[0062]
(Creation of adhesive sheet)
  Except for using the adhesive, RealA pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
[0063]
(Creation of adhesive sheet)
  As the adhesive, a commercially available general-purpose acrylic ester adhesive (trade name: L-145 / Nippon Carbide) was used., RealA pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.
[0064]
The pressure-sensitive adhesive and pressure-sensitive adhesive sheet prepared as described above were subjected to the following measurements and evaluations, and the results obtained are shown in Table 1.
[0065]
<Measurement item>
[Water swelling ratio]
The swelling ratio of the pressure-sensitive adhesive layer with respect to water was measured by the following method.
Use a commercially available polyester film (thickness 50 μm) for the surface substrate and a commercially available polyethylene laminate release paper for the release paper, and dry the adhesive to a dry weight of 25 g / m.²An adhesive sheet was prepared as follows. Thereafter, the release paper is removed, and the laminate of the polyester film and the pressure-sensitive adhesive layer is immersed in tap water at 20 ° C. for 1 hour. The thickness of the pressure-sensitive adhesive film before and after immersion in water was measured, and the swelling rate was determined according to the following formula. (unit:%)
[0066]
[Equation 3]

[0067]
[Water-soluble fraction]
The water-soluble component content (water-soluble fraction) of the pressure-sensitive adhesive film was measured by the following method.
Using a commercially available polyester film (thickness 50 μm) as the surface base material and a commercially available polyethylene laminate release paper as the release paper, each adhesive is 25 g / m in dry weight.²An adhesive sheet was prepared as follows. Thereafter, the release paper is removed, and the laminate of the polyester film and the adhesive layer is immersed in tap water at 20 ° C. for 24 hours. Thereafter, the pressure-sensitive adhesive is completely removed from the polyester film by ultrasonic waves to form a pressure-sensitive adhesive dispersion. The pressure-sensitive adhesive dispersion was filtered through a glass filter, and the weight of the pressure-sensitive adhesive filtered and the weight of the paste that was dried in the filtered water and dissolved in water were determined, and the water-soluble fraction was determined according to the following formula. . (unit:%)
[0068]
[Expression 4]

[0069]
〔Breaking strength〕
The breaking strength of the adhesive film in water was measured by the following method.
First, solvent-type heavy release silicone release agent (trade name: LTC-350A / manufactured by Toray Dow Corning): 100 parts, catalyst (trade name: SRX-212 / manufactured by Toray Dow Corning) : 0.8 parts dry weight 0.5 g / m²The release sheet A is prepared by coating and heat curing so that the release sheet A is used, and the release sheet A is used except that a light release silicone release agent (trade name: LTC-300B / manufactured by Toray Dow Corning) is used. A release sheet B is prepared in the same manner as the preparation method. Next, the release sheet A, the pressure-sensitive adhesive layer, and the release sheet B are sequentially laminated to prepare a pressure-sensitive adhesive sheet. In this case, the coating amount of each pressure-sensitive adhesive layer is 100 g / m in dry weight.²To be.
[0070]
Next, the pressure-sensitive adhesive sheet obtained by the above method is cut into a shape having a width of 20 mm and a length of 120 mm, and further, the release sheet A and the release sheet B are peeled off to make a test piece of the pressure-sensitive adhesive layer. One hour after immersing the obtained test piece in water, the maximum load leading to the cutting of the pressure-sensitive adhesive layer film was measured according to the tensile strength measurement method of JISK-6301, and the breaking strength was calculated by the following formula. I asked. (Unit: kgf / cm²)
[0071]
[Equation 5]

In addition, the thickness of an adhesive layer test piece can be measured with the following method.
Thickness of pressure-sensitive adhesive layer = thickness of pressure-sensitive adhesive sheet− {thickness of release sheet A + thickness of release sheet B}
[0072]
<Evaluation items>
[Adhesive strength]
Adhesive strength was measured based on the method for measuring the normal adhesive strength of JIS-Z-0237 (unit: g / 25 mm).
[0073]
[Cohesive strength]
The cohesive force was measured in accordance with the method for measuring the normal holding force of JIS-Z-0237. And according to the following evaluation criteria according to the measurement result.
A: There was no weight drop for 60 minutes after the start of measurement.
○: The weight dropped between 5 minutes and 60 minutes after the start of measurement.
X: The weight fell between less than 5 after the start of measurement.
[0074]
[Recyclability]
Water is added to 50 g of the pressure-sensitive adhesive sheet so that the pulp concentration becomes 3%, and after 150,000 rotation processing with a TAPPI disintegrator, the pulp is dehydrated until the pulp concentration becomes 15%. Add 5 g of deinking agent (trade name DI-600 / manufactured by Kao Corporation) 10% strength solution 1.8 g each, leave it at 40 ° C. for 20 minutes, and then dehydrate it until the pulp concentration reaches 25% Then, 3.62 g of 18% NaOH aqueous solution, 3.85 g of 30% Na2 SiO3 aqueous solution and 5 g of 6% H2 O2 water were added, respectively, and then kneaded for 5 minutes with a double arm kneader. went.
[0075]
Next, after being left for 120 minutes while maintaining at 55 ° C., it was diluted with water until the pulp concentration became 17.5%, and then the second kneading treatment was performed in the same manner. Thereafter, it was further diluted with water until the pulp concentration reached 1%. Next, this 1% -concentration pulp dispersion was subjected to flotation separation for 10 minutes using a flowmeter. The floating separation treatment liquid obtained by removing bubbles generated at that time with a scraper was further washed with 800 ml of water and dehydrated to a concentration of 13%. Water was added to the pulp dispersion thus obtained to a concentration of 0.3% to prepare a handsheet, and the remaining state of undissolved material was visually observed and judged according to the following evaluation criteria.
[0076]
(Recyclability evaluation criteria)
A: There is no adhesive foreign matter.
○: There are only a few adhesive foreign substances of several microns, but there is no practical problem.
△: There is no adhesive foreign material of 1 mm or more, but adhesive foreign material of several microns is conspicuous
This is a practical problem.
X: Adhesive foreign matter of 1 mm or more is quite noticeable.
[0077]
〔Comprehensive evaluation〕
The above evaluations were combined to evaluate the performance of the present invention as a recyclable adhesive sheet.
A: Used paper can be recycled as an adhesive sheet, and there is no practical problem in its adhesive performance.
X: Waste paper cannot be recycled as an adhesive sheet. Or, even though it is possible to recycle waste paper, its adhesive performance is poor and there is a problem in practical use.
[0078]
[Table 1]

[0079]
【The invention's effect】
As is clear from the results in Table 1, the pressure-sensitive adhesive sheet of the present invention has a property that the pressure-sensitive adhesive layer is easily adapted to water and further has a property that the film strength becomes brittle after being immersed in water. In the disaggregation process, the pressure-sensitive adhesive layer can be easily changed into fine particles, and can be easily removed from the pulp in each process such as fine selection, rough selection, and floatation. It was a pressure-sensitive adhesive sheet that could be used sufficiently in terms of adhesive performance.

Claims (2)

In the pressure-sensitive adhesive sheet having the surface base material and the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is (poly) ethylene glycol (meth) acrylate monomer 5 to 40% by weight, (meth) acrylic acid C _{4 to} C ₁₈ alkyl ester monomer 20 to 80 A pressure-sensitive adhesive comprising an ethylenically unsaturated carboxylic acid-containing monomer in an amount not exceeding 20% by weight and a copolymer of 1 to 40% by weight of a monomer copolymerizable with each of these monomers, and water adhesive sheet swelling ratio of 50% or more, 3 to 40 percent content of water-soluble component, the breaking strength after water immersion is characterized der Rukoto 2 kg / cm ² or less with respect to. The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer in which the particle size of the pressure-sensitive adhesive becomes a fine particle having a particle diameter of 1 mm or less when subjected to a 150,000-rotation treatment with a TAPPI disintegrator in a disaggregation step when recycling used paper. The pressure-sensitive adhesive sheet according to 1.